A moderator cannot BAN your account. They can ban you from posting on their subreddit, and can, often baselessly, get you reported to admins (who 100% of the time side with the moderators), usually flagging any kind of modmail conduct as "threatening or harassment". I've literally got a warning because I dared to ask a mod why they banned me - their response being a 30 day mute and a report to the admins about "Hey! I was wondering why you banned me, as I don't think my comment broke any of the rules of the sub or Reddit" being threatening, and harassment....