...assuming this is, in fact, a website issue and not PHPBB deciding that for some strange and unusual reason my posts require approval.
I wish I didn't have to assume it was censorship. Unfortunately, I can see no obvious reason for posts (and only my posts, it seems) to be delayed. If they never got posted, it could be a bug. But for something like this, the posting system would have to be more broken than Internet Explorer 6's HTML5 support, and nobody else would have to have noticed...or alternatively they have to be approved.