as I just commented above...
I think there was some change made down to how the site is translating markdown. when this was first brought to my attention, I thought it was a result of the hack, as my account was "compromised." however I was making a post today and ran into the same error - got the whole post cut off with a "/p>" - and determined that it was because I used the code "< center > and < /Center >" - and the capitalized letter threw off the translation.
unfortunately, I can't go back and edit this. not sure if that's still due to the account recovery process. hoping to figure it out soon, as this is a GREAT post I'll be referencing often. If I can't edit, I'll probably just end up reposting a duplicate....