I think its just our concious efforts to try and prevent rubbish being posted. Im sure we all agree the banter makes things fun, and we certainly wouldnt want to prevent the banter and chat from taking place.
Though there have been numerous examples of threads where they have deteriorated to such an extent they border on drivel. I believe the general policy on for sale items etc is to lock the topics after the item is sold or removed from sale etc, and on other threads, once they have reached a natural conclusion, perhaps they should be locked?
Ongoing issues that people suffer from perhaps shouldnt be locked, but if the additions to the topic for some time are pointless, then there is often little option, (other than to remove the offending indivisual posts, but then we get cries of censorship).
We have tried several methods of trying to remove the unnecessary (very off topic or ott) posts from threads, daily chat, chat rooms etc, but none seem to work. Preventing threads from becoming a mess in the forst place is just one more option that can be used, and clearly this appears to raise eyebrows too.