Akira: What's wrong with keeping old trade threads? And why is it more important to purge sales threads than any other threads? It's not like they're in the way of anything. On the contrary, keeping old sales threads saves the track record of each buyer and seller which might be interesting for future buyers/sellers.

Nobody is going to search thorough a person's threads to see their "track record", as far as I know, that's what the feedback thread is for.

If you purge you keep it fresh. You always have the latest 2 or 3 months worth of "trades" there. If the thread didn't receive any attention in 1 or 2 months (no user posts or < than a certain amount of views), it is pointless to keep it, the item(s) is/are probably traded, sold or bought already.
It will save space (doesn't matter) and also maybe help the search speed up (less shit to search through).

As to any other threads to purge, I don't see any parameter to safely purge automatically any other forum. They all possibly contain interesting info. But as I said, there's no interesting information in a thread about an item discarded of a year ago.

Akira: What's wrong with keeping old trade threads? And why is it more important to purge sales threads than any other threads? It's not like they're in the way of anything. On the contrary, keeping old sales threads saves the track record of each buyer and seller which might be interesting for future buyers/sellers.

edit: spelling

I don't see any reason to store those messages and that way messages keep fresh. Having just one thread by user forever is a bit pointless.

Also, to be honest, I NEVER check the first post except when it was created. If it gets updated, I don't care about going back to the first page (Specially on collaboration threads)

Editing is a must in my opinion

Editing your first post if you've made the thread can be quite important (for updates to gig threads, for instance) so it would be a shame to have to start a new thread and start clogging up the forums (and adding to the workload of mods having to delete old threads) because some forum members are unable to act maturely.

This is also important for collaboration threads or releases.  In the case you want to add album artwork or a track/artist list into the first post.  There could be a sort of permission rule so that moderators have to do the editing or change the users permissions temporarily so they can edit their posts but this would cause a huge workload for the mods and admins and also be kind of annoying.... Although I definitely see the reason for Akira's concern.

Editing your first post if you've made the thread can be quite important (for updates to gig threads, for instance) so it would be a shame to have to start a new thread and start clogging up the forums (and adding to the workload of mods having to delete old threads) because some forum members are unable to act maturely.

Otherwise retarded shit like what this kid has done can occur and end up in thread destroying.
I can go back to my first post and edit it, which is pretty intense. I could erase the content in all my posts if I wished so.

It can also be used to tergiverse arguments.