It's very possible that some of them must have engaged themselves in doing this, or even organize a group where they routinely give each other positive Karma, whether post deserve it or not.
great analysis.
I have no doubt from your postulation but I think giving karma to a good post is worth it and serves as a means of encouraging more good posts and contributions as well. I believe admin has control and oversee everything going on here so, possibly that must have warranted his actions as the accounts must have been abusing the karma rules here. I love the way admin handled the situation without any observations and issues as that would have raised concerns here.
Well, there was no way the issue of an erased karma would or should have been handled without any observations, at least, this thread is a proof to the fact that I observed it, and that was why I decided to create this thread to find out why or what happened.
And I agree any way, for admin said something I liked when we wanted to know how this user(now users) abused the karma system, the admin didn't answer, he simply said that the wiped karma is already a harsh punishment, there is no need shaming the user by stating exactly what they did.
And talking about giving good posts Karma, there was never a time doing so was bad, you can give karma to as much good posts as you see when you come around them, but what the admin Is against is, abusing it, like Karma exchange and so on.