They fixed this on Dreamwidth (http://bugs.dwscoalition.org/show_bug.cgi?id=1358) and the patch has been migrated upstream to LJ (http://community.livejournal.com/changelog/7408601.html), so you won't be able to do it here anymore soon.

(By this, I mean use a comment to trollishly wallpaper an entry, not prevent people from posting pics of bukkake. We're good, but we're not that good.)