I agree with @hawk that someone will need to reach out to the admins/owners.
These type of people are toxic for both forums, regardless if they follow the rules on one but not the other.
Just having these two on their forum makes them also guilty by association of these 2 users.
a moderator is the face of an forum and their actions on any other platform reflects good or bad on any other medium.
I will immediately remove these types of people as their actions are questionable.