I comment, quote and joke around in FS threads all the time. I also spend at least a grand a month on here. You can always go to ebay to buy and sell, no chatter or community there. You wont even have to be polite to anyone.
You're missing the point by about a mile.
I'm not complaining about a little banter in a sales thread - what is annoying, though, is people posting drivel to either drive up their post count or just because they can. Does every modern sales thread really need 15 posts of "moar" & popcorn, and random pictures of either fatties or cheerleaders - particularly when those posts push down the sales threads where the seller is actually posting books?
I am guilty of this, but its more my way of encouraging a seller when they say they are going to posts more books to actually post them if I think they have something I would be interested in. I started doing it when I would read a sellers post saying "XXXXXX is coming up", but then wouldn't get to XXXXX because sales were poor on their other books.