And maybe following on from this thread:
https://www.jamroom.net/the-jamroom-network/forum/using-jamroom/32890/allowed-html-tags-fail-validation-on-shared-profile
The problem I was seeing wasn't to do with a shared profile, but I have found the same thing happening here on jamroom.net, you can reproduce it like this:
Update a forum post, add this html to the textarea:
<ul><li>asdfa</li></ul>

Update the forum post again with a line break in the html like this:
<ul> <li>asdfa</li></ul>

Update the forum post again with the line break in after the list item like this:
<ul><li>asdfa</li> </ul>

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updated by @ultrajam: 02/24/16 11:56:01PM