I was experimenting with the "personal statement" field of my Careers profile and found that I could seemingly get fairly fancy with embedded HTML because it displayed nicely in the preview. Upon saving it though it was all stripped leaving just a run-on paragraph. "Wow!" I thought to myself, "that appears to be quite a major gaff with SO... so what am I missing?" Well, immediately below the field it states "This text field supports Markdown formatting." Following the link to the Markdown web pages, I went to the Syntax page and the Inline HTML section. It states "For any markup that is not covered by Markdown’s syntax, you simply use HTML itself." and goes on to state that the only restrictions involve whitespace considerations. Thus, following the available information, my HTML tables and divs should have worked.
Before posting a "Hey, I found a huge bug, folks!" I delved further and found What HTML tags are allowed on Stack Overflow, Server Fault, and Super User? that talks about, as you likely know, which HTML tags are permitted on SO sites. It even directly addresses my conundrum: "HTML tags not on this list are stripped from the output. They may render in the client preview but they will always be removed on the server."
My point here is that the system as it stands now leads users to a roadblock and/or a source of frustration. It goes against the driving principle of SO -- to make things delightfully easy for the user.
My call to action, then, is simply to change the text below the field from this:
This text field supports Markdown formatting.
This text field supports Markdown formatting *with limitations*.
... with limitations linked to the MSO FAQ link given above.