2. Based on my research, those accounts already got banned. Why does moderators ban those accounts? it's temporary or permanent? AFAIK most accounts got banned due to plagiarism or evading ban, not spamming.
You are not most likely going to get banned for spamming a single time. If you spam a lot, you will get banned of course. The above mentioned users have no contribution on the forum, most of their post are spam. It can be safely assumed that they will only bring spam to the forum, nothing else. Having them banned makes sense I think.