But maybe considering a really large amount of similar threads, it would be a good solution to create a Child Board especially for this... I think it could clean a bit Meta board...
Just like you said and rule number 25 states that a banned user/account is only allowed to make a single thread here in meta about his/her ban
And that's exactly what this users/members did/are doing,and I do not see anything wrong in it, probably making more than one thread or persistently commenting on the thread made,then it's definitely against the rules
Having numerous threads about it is acceptable considering the fact that it's the right section for it, I guess we're having more of it because our MODs are cracking down on more cheaters,copy/past posters and plagiarist saving Tman the stress of swearing at them..