There's no way there should be a thread "look at this car what a load of crap" but to my mind "look at the exhausts on this" is ok even if the photo was taken without permission (and the barries will confirm this is all legal of course). After that, posts saying "I don't like it" seems ok to me but not "what idiot would do that" or somesuch.
It's a fine line though - and I guess the people who own the site get to chose where to draw it. However, to avoid threads like this one, surely it would be good to give a reason for deletion (as I'#ve seen on many forums) rather than just have it gone, which is annoying. Especially since I've spent time searching every section for a thread before now not knowing it'd gone! Anyway this must be possible it happens on PSC and, er, briskoda.