First of all, my sincere apologies if this is a duplicate.
The problem, in short: WordPress inserted a number of unclosed <p> tags into my post. It should either insert correctly closed tags, or none at all. I honestly would prefer the former.
In detail: I had HTML code very similar to this:
<ul>
<li>text<ul>
<li>subtext</li>
</ul>more text</li>
</ul>
This was automatically converted to:
<ul>
<li>text<ul>
<li>subtext</li>
</ul><p>more text</li>
</ul>
Note the extra <p> tag in the above, which is unclosed (making the W3C validator choke on my website).
Also note, I was not using the WYSIWYG editor (turning it off was the first thing I did), so it's unlikely to be due to that.
As a workaround, manually inserting properly closed <p> tags works just fine:
<ul>
<li>text<ul>
<li>subtext</li>
</ul><p>more text</p></li>
</ul>
Since this workaround exists, the bug is not very prioritary, but it should also (hopefully) be easy to fix.
