Your logic is invalid. As mentioned in other threads on here, some people are creating accounts via bots. They could probably create accounts and post faster then you can "ban" a user.
No it isn't. Trolls aren't really using bots to create their accounts; those tend to just be spambots and the user can just ban them as fast too, but that's their prerogative, but you could make the same argument about self-modded threads.
I would think, at least in theory that most of the trolls are trolling other alt coins because they want to destroy the competition. If they had to resort to using bots then they may do so. Although I admit this argument is somewhat weak.
Additionally you are lacking a non-scam use of this proposed feature. If someone is actually breaking the rules then you can report the posts for a moderator to take action against them, or you can send a PM to a mod, or you can create a thread here about their activity.
Again, no I'm not. Are you proposing there's no non-scammy reason to self-mod a thread?
There are very few non-scammy reasons to create a self moderated thread. The most responsible way to do so is to make your own post of what you delete, or otherwise preserve what is deleted for public view.
this is an example of this.
There are other reasons to delete messages on self moderated threads that are legit but they are few and far between.
Trolls who repeatedly post in someones thread can be banned if they've been told not to and this would cut work out for the mods who don't have to deal with such petty instances.
I would say if someone is truly breaking the rules then they should be dealt with by the mods (e.g. with a forum ban) as if they troll one thread they will likely troll other threads as well.
Just because someone spams a thread one time does not mean they will repeatedly do so. That person should have the right to add something to the conversation at a later time. If the mods will ban someone for actually breaking the rules then there is no legit reason for someone to ban someone from a specific thread.
If we have self-modded threads then this isn't really much different and those who want to comment without censorship will just do so in a new thread just like they do with self-modded ones they want to freely comment on.
Well it makes it more difficult for someone like tomatocage or Vod (or the altcoin equivalent) to warn others about a potential scam. If someone were to create an uncensored version of a scam coin then it may not get posted in as much so it would quickly get lost while the self moderated thread would remain active.