I've written a patch adding support for optional ends tags (issue 29218). I've mailed simon mourier, but didn't get a reply; I'm assuming he's no longer the maintainer or the email is out of date.
The patch should allow parsing things like unclosed <p> and <li> tags and still get the correct parse tree (the current implementation leaves unclosed <p> tags empty, and nests unclosed <li> tags). A review would be appreciated,
and hopefully a merge, eventually.
I've attached the patch to issue 29218: http://htmlagilitypack.codeplex.com/workitem/29218
So what do you think?