diff --git a/MANIFEST.in b/MANIFEST.in
index 9561fb1..70656c8 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1 +1,2 @@
 include README.rst
+prune tests
diff --git a/README.rst b/README.rst
index 51888ea..55ea7cf 100644
--- a/README.rst
+++ b/README.rst
@@ -1,8 +1,8 @@
 |build| |version| |license| |downloads|
 
-.. |build| image:: https://img.shields.io/github/workflow/status/matthewwithanm/python-markdownify/Python%20application/develop
+.. |build| image:: https://img.shields.io/github/actions/workflow/status/matthewwithanm/python-markdownify/python-app.yml?branch=develop
     :alt: GitHub Workflow Status
-    :target: https://github.com/matthewwithanm/python-markdownify/actions?query=workflow%3A%22Python+application%22
+    :target: https://github.com/matthewwithanm/python-markdownify/actions/workflows/python-app.yml?query=workflow%3A%22Python+application%22
 
 .. |version| image:: https://img.shields.io/pypi/v/markdownify
     :alt: Pypi version
@@ -87,7 +87,11 @@ strong_em_symbol
 sub_symbol, sup_symbol
   Define the chars that surround ``<sub>`` and ``<sup>`` text. Defaults to an
   empty string, because this is non-standard behavior. Could be something like
-  ``~`` and ``^`` to result in ``~sub~`` and ``^sup^``.
+  ``~`` and ``^`` to result in ``~sub~`` and ``^sup^``.  If the value starts
+  with ``<`` and ends with ``>``, it is treated as an HTML tag and a ``/`` is
+  inserted after the ``<`` in the string used after the text; this allows
+  specifying ``<sub>`` to use raw HTML in the output for subscripts, for
+  example.
 
 newline_style
   Defines the style of marking linebreaks (``<br>``) in markdown. The default
@@ -123,6 +127,11 @@ escape_underscores
   If set to ``False``, do not escape ``_`` to ``\_`` in text.
   Defaults to ``True``.
 
+escape_misc
+  If set to ``False``, do not escape miscellaneous punctuation characters
+  that sometimes have Markdown significance in text.
+  Defaults to ``True``.
+
 keep_inline_images_in
   Images are converted to their alt-text when the images are located inside
   headlines or table cells. If some inline images should be converted to
diff --git a/markdownify/__init__.py b/markdownify/__init__.py
index 86226d2..cd66a39 100644
--- a/markdownify/__init__.py
+++ b/markdownify/__init__.py
@@ -43,15 +43,22 @@ def abstract_inline_conversion(markup_fn):
     """
     This abstracts all simple inline tags like b, em, del, ...
     Returns a function that wraps the chomped text in a pair of the string
-    that is returned by markup_fn. markup_fn is necessary to allow for
+    that is returned by markup_fn, with '/' inserted in the string used after
+    the text if it looks like an HTML tag. markup_fn is necessary to allow for
     references to self.strong_em_symbol etc.
     """
     def implementation(self, el, text, convert_as_inline):
-        markup = markup_fn(self)
+        markup_prefix = markup_fn(self)
+        if markup_prefix.startswith('<') and markup_prefix.endswith('>'):
+            markup_suffix = '</' + markup_prefix[1:]
+        else:
+            markup_suffix = markup_prefix
+        if el.find_parent(['pre', 'code', 'kbd', 'samp']):
+            return text
         prefix, suffix, text = chomp(text)
         if not text:
             return ''
-        return '%s%s%s%s%s' % (prefix, markup, text, markup, suffix)
+        return '%s%s%s%s%s' % (prefix, markup_prefix, text, markup_suffix, suffix)
     return implementation
 
 
@@ -69,6 +76,7 @@ class DefaultOptions:
         default_title = False
         escape_asterisks = True
         escape_underscores = True
+        escape_misc = True
         heading_style = UNDERLINED
         keep_inline_images_in = []
         newline_style = SPACES
@@ -199,6 +207,9 @@ def should_convert_tag(self, tag):
     def escape(self, text):
         if not text:
             return ''
+        if self.options['escape_misc']:
+            text = re.sub(r'([\\&<`[>~#=+|-])', r'\\\1', text)
+            text = re.sub(r'([0-9])([.)])', r'\1\\\2', text)
         if self.options['escape_asterisks']:
             text = text.replace('*', r'\*')
         if self.options['escape_underscores']:
@@ -315,7 +326,7 @@ def convert_list(self, el, text, convert_as_inline):
     def convert_li(self, el, text, convert_as_inline):
         parent = el.parent
         if parent is not None and parent.name == 'ol':
-            if parent.get("start"):
+            if parent.get("start") and str(parent.get("start")).isnumeric():
                 start = int(parent.get("start"))
             else:
                 start = 1
@@ -377,13 +388,13 @@ def convert_figcaption(self, el, text, convert_as_inline):
 
     def convert_td(self, el, text, convert_as_inline):
         colspan = 1
-        if 'colspan' in el.attrs:
+        if 'colspan' in el.attrs and el['colspan'].isdigit():
             colspan = int(el['colspan'])
         return ' ' + text.strip().replace("\n", " ") + ' |' * colspan
 
     def convert_th(self, el, text, convert_as_inline):
         colspan = 1
-        if 'colspan' in el.attrs:
+        if 'colspan' in el.attrs and el['colspan'].isdigit():
             colspan = int(el['colspan'])
         return ' ' + text.strip().replace("\n", " ") + ' |' * colspan
 
@@ -400,7 +411,7 @@ def convert_tr(self, el, text, convert_as_inline):
             # first row and is headline: print headline underline
             full_colspan = 0
             for cell in cells:
-                if "colspan" in cell.attrs:
+                if 'colspan' in cell.attrs and cell['colspan'].isdigit():
                     full_colspan += int(cell["colspan"])
                 else:
                     full_colspan += 1
diff --git a/setup.py b/setup.py
index 9a26468..9a703d0 100644
--- a/setup.py
+++ b/setup.py
@@ -9,7 +9,7 @@
 pkgmeta = {
     '__title__': 'markdownify',
     '__author__': 'Matthew Tretter',
-    '__version__': '0.12.1',
+    '__version__': '0.13.0',
 }
 
 read = lambda filepath: codecs.open(filepath, 'r', 'utf-8').read()
diff --git a/tests/test_conversions.py b/tests/test_conversions.py
index 1e685f3..a35b982 100644
--- a/tests/test_conversions.py
+++ b/tests/test_conversions.py
@@ -87,6 +87,16 @@ def test_code():
     assert md('<code><span>*this_should_not_escape*</span></code>') == '`*this_should_not_escape*`'
     assert md('<code>this  should\t\tnormalize</code>') == '`this should normalize`'
     assert md('<code><span>this  should\t\tnormalize</span></code>') == '`this should normalize`'
+    assert md('<code>foo<b>bar</b>baz</code>') == '`foobarbaz`'
+    assert md('<kbd>foo<i>bar</i>baz</kbd>') == '`foobarbaz`'
+    assert md('<samp>foo<del> bar </del>baz</samp>') == '`foo bar baz`'
+    assert md('<samp>foo <del>bar</del> baz</samp>') == '`foo bar baz`'
+    assert md('<code>foo<em> bar </em>baz</code>') == '`foo bar baz`'
+    assert md('<code>foo<code> bar </code>baz</code>') == '`foo bar baz`'
+    assert md('<code>foo<strong> bar </strong>baz</code>') == '`foo bar baz`'
+    assert md('<code>foo<s> bar </s>baz</code>') == '`foo bar baz`'
+    assert md('<code>foo<sup>bar</sup>baz</code>', sup_symbol='^') == '`foobarbaz`'
+    assert md('<code>foo<sub>bar</sub>baz</code>', sub_symbol='^') == '`foobarbaz`'
 
 
 def test_del():
@@ -215,6 +225,17 @@ def test_pre():
     assert md('<pre><span>*this_should_not_escape*</span></pre>') == '\n```\n*this_should_not_escape*\n```\n'
     assert md('<pre>\t\tthis  should\t\tnot  normalize</pre>') == '\n```\n\t\tthis  should\t\tnot  normalize\n```\n'
     assert md('<pre><span>\t\tthis  should\t\tnot  normalize</span></pre>') == '\n```\n\t\tthis  should\t\tnot  normalize\n```\n'
+    assert md('<pre>foo<b>\nbar\n</b>baz</pre>') == '\n```\nfoo\nbar\nbaz\n```\n'
+    assert md('<pre>foo<i>\nbar\n</i>baz</pre>') == '\n```\nfoo\nbar\nbaz\n```\n'
+    assert md('<pre>foo\n<i>bar</i>\nbaz</pre>') == '\n```\nfoo\nbar\nbaz\n```\n'
+    assert md('<pre>foo<i>\n</i>baz</pre>') == '\n```\nfoo\nbaz\n```\n'
+    assert md('<pre>foo<del>\nbar\n</del>baz</pre>') == '\n```\nfoo\nbar\nbaz\n```\n'
+    assert md('<pre>foo<em>\nbar\n</em>baz</pre>') == '\n```\nfoo\nbar\nbaz\n```\n'
+    assert md('<pre>foo<code>\nbar\n</code>baz</pre>') == '\n```\nfoo\nbar\nbaz\n```\n'
+    assert md('<pre>foo<strong>\nbar\n</strong>baz</pre>') == '\n```\nfoo\nbar\nbaz\n```\n'
+    assert md('<pre>foo<s>\nbar\n</s>baz</pre>') == '\n```\nfoo\nbar\nbaz\n```\n'
+    assert md('<pre>foo<sup>\nbar\n</sup>baz</pre>', sup_symbol='^') == '\n```\nfoo\nbar\nbaz\n```\n'
+    assert md('<pre>foo<sub>\nbar\n</sub>baz</pre>', sub_symbol='^') == '\n```\nfoo\nbar\nbaz\n```\n'
 
 
 def test_script():
@@ -247,11 +268,13 @@ def test_strong_em_symbol():
 def test_sub():
     assert md('<sub>foo</sub>') == 'foo'
     assert md('<sub>foo</sub>', sub_symbol='~') == '~foo~'
+    assert md('<sub>foo</sub>', sub_symbol='<sub>') == '<sub>foo</sub>'
 
 
 def test_sup():
     assert md('<sup>foo</sup>') == 'foo'
     assert md('<sup>foo</sup>', sup_symbol='^') == '^foo^'
+    assert md('<sup>foo</sup>', sup_symbol='<sup>') == '<sup>foo</sup>'
 
 
 def test_lang():
diff --git a/tests/test_escaping.py b/tests/test_escaping.py
index 2f3a83e..eaef77d 100644
--- a/tests/test_escaping.py
+++ b/tests/test_escaping.py
@@ -12,7 +12,7 @@ def test_underscore():
 
 
 def test_xml_entities():
-    assert md('&amp;') == '&'
+    assert md('&amp;') == r'\&'
 
 
 def test_named_entities():
@@ -25,4 +25,23 @@ def test_hexadecimal_entities():
 
 
 def test_single_escaping_entities():
-    assert md('&amp;amp;') == '&amp;'
+    assert md('&amp;amp;') == r'\&amp;'
+
+
+def text_misc():
+    assert md('\\*') == r'\\\*'
+    assert md('<foo>') == r'\<foo\>'
+    assert md('# foo') == r'\# foo'
+    assert md('> foo') == r'\> foo'
+    assert md('~~foo~~') == r'\~\~foo\~\~'
+    assert md('foo\n===\n') == 'foo\n\\=\\=\\=\n'
+    assert md('---\n') == '\\-\\-\\-\n'
+    assert md('+ x\n+ y\n') == '\\+ x\n\\+ y\n'
+    assert md('`x`') == r'\`x\`'
+    assert md('[text](link)') == r'\[text](link)'
+    assert md('1. x') == r'1\. x'
+    assert md('not a number. x') == r'not a number. x'
+    assert md('1) x') == r'1\) x'
+    assert md('not a number) x') == r'not a number) x'
+    assert md('|not table|') == r'\|not table\|'
+    assert md(r'\ <foo> &amp;amp; | ` `', escape_misc=False) == r'\ <foo> &amp; | ` `'
diff --git a/tests/test_lists.py b/tests/test_lists.py
index 5a04430..35eee13 100644
--- a/tests/test_lists.py
+++ b/tests/test_lists.py
@@ -43,6 +43,9 @@
 def test_ol():
     assert md('<ol><li>a</li><li>b</li></ol>') == '1. a\n2. b\n'
     assert md('<ol start="3"><li>a</li><li>b</li></ol>') == '3. a\n4. b\n'
+    assert md('<ol start="-1"><li>a</li><li>b</li></ol>') == '1. a\n2. b\n'
+    assert md('<ol start="foo"><li>a</li><li>b</li></ol>') == '1. a\n2. b\n'
+    assert md('<ol start="1.5"><li>a</li><li>b</li></ol>') == '1. a\n2. b\n'
 
 
 def test_nested_ols():
diff --git a/tests/test_tables.py b/tests/test_tables.py
index 9120c29..594e5bf 100644
--- a/tests/test_tables.py
+++ b/tests/test_tables.py
@@ -215,7 +215,7 @@
         <th>Age</th>
     </tr>
     <tr>
-        <td>Jill</td>
+        <td colspan="1">Jill</td>
         <td>Smith</td>
         <td>50</td>
     </tr>
@@ -226,6 +226,17 @@
     </tr>
 </table>"""
 
+table_with_undefined_colspan = """<table>
+    <tr>
+        <th colspan="undefined">Name</th>
+        <th>Age</th>
+    </tr>
+    <tr>
+        <td colspan="-1">Jill</td>
+        <td>Smith</td>
+    </tr>
+</table>"""
+
 
 def test_table():
     assert md(table) == '\n\n| Firstname | Lastname | Age |\n| --- | --- | --- |\n| Jill | Smith | 50 |\n| Eve | Jackson | 94 |\n\n'
@@ -240,3 +251,4 @@ def test_table():
     assert md(table_body) == '\n\n| Firstname | Lastname | Age |\n| --- | --- | --- |\n| Jill | Smith | 50 |\n| Eve | Jackson | 94 |\n\n'
     assert md(table_with_caption) == 'TEXT\n\nCaption\n| Firstname | Lastname | Age |\n| --- | --- | --- |\n\n'
     assert md(table_with_colspan) == '\n\n| Name | | Age |\n| --- | --- | --- |\n| Jill | Smith | 50 |\n| Eve | Jackson | 94 |\n\n'
+    assert md(table_with_undefined_colspan) == '\n\n| Name | Age |\n| --- | --- |\n| Jill | Smith |\n\n'
diff --git a/tox.ini b/tox.ini
index 9eb8750..54ba143 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,7 +4,7 @@ envlist = py38
 [testenv]
 passenv = PYTHONPATH
 deps =
-	pytest
+	pytest==8
 	flake8
 	restructuredtext_lint
 	Pygments