And who decides what is pointless or not?By the OP, and it's just a tag added to the title, the thread isn't closed. It has value for those looking to help, because they can immediately see that the OP has got his/her answer. Anyone with a similar problem or with additional/useful information can still post if they want to.
No forum ever allows that, only admins or mods can edit or remove other posters' content. You can only ever edit your own posts. Some lock you out of editing the first post after there have been replies. An OP who deletes the first post obviously destroys the thread.
I don't think any user can move threads-if they want to go off on a tangent, they can start a new thread elsewhere. I've never seen any notes section, but I don't think it should ever be necessary to try to extract information from the forum because it's buried in 'chat'.
I would find it annoying. It shouldn't be hard for people to modify their behaviour and not post pointless replies.
Sure, that's not a problem. It's when somebody comes in and pipes up with something that's been said earlier in the thread, sometimes many times, by many different posters. Sometimes, it's not even in a long thread and it's obvious that the poster hasn't bothered reading anything anyone else has posted. (again, not necessarily on this forum, but it happens relatively frequently.) Some people see forums more as QandA and don't bother with reading other replies at all.