Ironically Onlyfans have really good systems for this. All communication is monitored and any mention of blackmail (including indirect references) will get the sending account banned.
The blackmail risk is actually fairly balanced between content creators and subscribers. If you look on Twitter for example, you'll see loads of adult content creators blackmailing their customers.
AFAIK Onlyfans doesn't directly purse blackmail cases with its own legal teams, it just bans accounts.