>>99990490make it where the client has to have a unique certificate before posting. Meaning you start off with like 1,000 for the first people who show up. From there they have to generate new certificated signed with their own to invite other people to the board.
Not only for gatekeeping, but also banning. You could temporarily or permanently ban someone's certificate, and if you wanted, their child certificates as well.
Also porn and lewd pics should be banned on all boards that aren't porn boards.