We need to nominate a dude to the mod team for the EXPRESS purpose of banning this weirdo's alts. I'm grateful to u/DomitiusofMassilia for popping in every few days, but sadly that's not frequent enough. We need a daily reader who can just hit "ban" when he's browsing comments. It won't solve the problem but it'll alleviate it.
We could also freeze new account creation and open it for select periods, announced with pinned posts. Our growth would be disrupted of course, but it's not like that matters that much.
Going by what others have said most of these accounts from the spammer are old ConPro accounts that have since been banned from there and wherever else, but were never active on this board which is why it's accounts that are 1 year old but still have the handshake. Handshakes don't indicate account age, it's an engagement score.
Someone could make a new account today and do everything correct with posts and comments and lose their handshake within the week. Whereas week old, or longer, accounts that are blatant trolls and only ever get downvoted aren't likely to ever have it happen.