That the system doesn't let you know that you're still banned even if your 6-month limit has opened up is a common source of confusion. I've filed a feature request on our general meta site asking for that to be fixed; you may consider supporting it.

So, as far as I can read the question and your answer, as well as all comments, the user was (in your opinion validly) suspended for casting an incorrect migration close vote. Since you didn't mention so in your answer, were there other concerns at play, other than the incorrect close vote, which led to the suspension (don't have to disclose those)?

Yeah, I did make a request several years ago to have the required reputation to create tags raised, but that was de-facto declined.

@Burgi But having to do that repeatedly so many times is a big pain. There's also no way to be notified when a tag is recreated (watcher lists are cleared when a tag is removed), so only when someone checks infrequently and notices will it get cleared, and in the meantime, it will continue to be used on other questions by others (who may not read the description) and increase the effort (and home page impact) required to remove the tag. A similar situation happened with the google tag, and it was blacklisted for this same reason.

@Mokubai Questions with only zero- or negatively-scored answers can still be eligible for deletion as RemoveAbandonedClosed. Those are not necessarily exempt from automatic deletion. The purpose of this question is for the community to discuss whether or not they should be deleted (after all, merely qualifying for automatic deletion doesn't necessarily mean it should be deleted). The request for SE to fix this is already posted on the global meta.