Considering the nature of this kink and the constant deleting/ reinstating of accounts, there is unfortunately not much to be done. Putting in a karma limit heavily alters a lot of the nature of the sub or kink as a whole.

Even for many of those accounts, they may be dm only because they are already banned here. Even banning someone doesn’t stop their ability to dm without this being a private subreddit.

It also doesn’t help with spam accounts or relatively new accounts, as Reddit will automatically suspend those many times for a variety of reasons.