I’ve been locked out of one forum for many years now, by my good friend Rob. No cool down period, no fixed period, just locked out. A request for a review of «my case» was met with no understanding. It’s their train set, so they get to do what they want to, but it’s a weird way to moderate.
For the OP,
AFAIK GDPR says you should have an easy way to leave a site/forum/mail list.
The question is if GDPR applies since this site is not based in Europe. Or is it?