Grounds for appeal, generally not (or generally not required). Users can technically make a moderation complaint and that will then get passed up the chain to Site Administrators (financial owners/backers, and coders/server owners), but most often trust is put in moderators to make the right call. These days most actions against a user are taken in consultancy with several site moderators in agreeance.
With that said:
On shorter bans you are "Sin Binned", which means you can still PM, you just can't post in threads.
On longer bans though, you are "Sin Binned" as well as "Banned", meaning you have no forum access at all and can only view as a guest.
We also have the ability to Lifetime Ban with / without appeal.
Moderators have held several conversations over the past 6 months about Nab Fabs approach towards posting and despite warnings and previous bans it fell on deaf ears. You can only warn someone so much before action needs to be taken.
His manner of posting is that someone offers an opinion. That opinion differs so he'll argue and disrupt a thread, forcing his opinion on others. When a disagreeance in opinion continues, he then becomes abusive at fellow users. That then develops into a flamewar/shitfight, and mods then need to spend lengthy periods cleaning up (or reconstructing) a thread. Then there's beating a dead horse (no offence
@Horse) with the same comment all the time (anti Foran, anti Pay). In the 2018 season it was anti another player. Before that it was anti another player.
It gets tiresome. If you hate the players and hate the club so much, why are you even here!?!
He needs to accept others opinions (we've told him that before), and not to aggressively react to differences of opinion.