It may be too late to influence the consensus decision here, but I'm one of the people downvoted, so what the hell.

As one of the users who was targeted - I don't know who by yet, it may have been a different person to [REDACTED 2] - I'm much more interested in being able to ask why and get new information. That is, after all, the purpose of the karma system, no? To provide information?

Sure, it feels shitty to be suddenly subject to various anti-troll measures because some anonymous individual apparently finds you sub-par. Seriously, it does. It messes up the entire karma system to have people doing this, and it seems to have been empirically driving away surprising numbers of users.

But will banning people who didn't realize that - who acted in good faith, and didn't know that they were breaking any rules because the rules didn't exist yet - really help prevent that?

If we want to "send a message" that this will not be tolerated - which is the whole purpose of reward/punishment systems, no? - surely a simple top-level announcement will suffice? All banning the perpetrator(s) will do is ... ban them. Remove them from the site. Users, I may note, who must have been productive, high-karma users in order to be capable of downvoting so many posts.