Sorry for the late response!
If the previous implementation was re-added as an option, I believe this would entirely solve the gmail issue. At least in my case. It’s quite perfect in my opinion and adds enough resource costs to the spammers to make fighting it manageable. It’d really be the difference between requiring 24hr full time high intensity moderation and not.
I’ve blocked several domains that allow similar and make use of the allowed email domains list. The problem is that people can create many accounts prior to getting one of their accounts banned/blocked (which activates the blocking of permutations of that gmail address for new accounts, but existing accounts are left untouched). Making it quite a burden for moderation and tedious to clean up each individual account afterwards.
For example I’ve had a thread that had ~200 or so replies, using 1 post per account, all made with the same gmail address. A lot of similar cases. These being an example where the accounts are easy to find, as searching for them via permutations of the original gmail is really difficult as an alternative. Some will farm a large amounts of accounts using a small handful of gmails and not post on them until months later.
For regex blocking as a solution, blocking + signs would be fairly harmless, periods (.) would likely block a significant amount of legit emails i.e. john.smith@gmail.com. Blocking addresses with more than one period would probably have minimal collateral damage, though would still allow several permutations of a gmail address, but much less than with 2+ periods.
IMO the previous implementation is ideal and not unreasonable to implement as an optional protection, most popular social sites won’t allow signing up using several gmail permutations due to it being heavily exploited by spammers.
Thanks 