Look at the linked profiles and at the comments they posted. If you go back far enough, the sea of dead comments (turn showdead on) will stop and you will see comments with up- and downvotes as well as responses. That’s when they were banned, so the reason must be somewhere there.

I couldn’t find it, though. Seems arbitrary to me. Looks like commenters with slightly below average quality contributions who wouldn’t be missed by anyone were banned.