There are very old unused discussions are in the forum... can it be deleted. So that the forum will be clean.
Let people start some some new usefull topics...
Why do you need to delete them. If no-one posts in them, they will eventually move into the next pages of the forum, where they are hidden from view anyway. And even if someone does post in them, a mod will simply lock them, and they will eventually move out of view as well.
There is also the amount of time that this will take to go through the numerous topics there aren't being used and delete them all one by one. I'm pretty sure the mods don't want to spend their time doing this, frankly boring job, when they could be moderating the topics that are being used, which would be a lot more useful to everyone else.
If you have any examples of topics you think should be deleted post them here, but overall i'd have to disagree with you.
there was a suggestion like this before. The suggestion was to use the (inbuild) prune function to remove all old posts. This would remove the old posts.
The reason we don't do this is because we want to keep our old topic. Some contain info that might help other users, some contain stuff we want to keep because we linked to it in other topics, and some are kept for other reasons.
We don't lock topics because someone bumps them, we lock them if we don't think nothing useful can be added (question solved, problem solved, server back up,...) or when we expect the topic to attract useless posts.
There is nothing stopping people doing this already and rvec has just explained why Frihost doesn't prune topics/posts.