characters being deleted when using invalid HTML

Hi all,
I’ve just noticed this when I accidentally forgot to close an li tag in my HTML. When I posted the page, WordPress actually correctly closed the li tag for me in the right place, but some characters appearing after the tag were deleted.
Example:
I have a page of lists. Each one starts with a paragraph (with opening and closing p tags). After each one is an unordered list (ul) with many li’s. If I leave one li open, it gets closed, but a few characters afterwards are deleted. If you need an example of this HTML page, you can have a look at the changelog on my site.