I have noticed that while most communities that I have seen allow you to appeal your ban sooner or later and are not that quick on banning people, there are some that do not allow any unban appeals and ban permanently. It is often combined with very strict rules that disallow, for example, criticizing anything, discussing banning policy, and couching new players to follow the rules (natural reaction to some situations of most people I have dealt with online) and/or vary ambiguous rules that are frequently used to justify bans of some behavior that is simply not liked by the admins.
And I have noticed that both "democracy-based" communities like SE and "censorship-based" communities like some forums actually can both yield very high-quality content.
So, I am asking if there are any advantages and disadvantages of permanently banning people for even the slightest rules violations and not allowing to appeal those bans?
My question is based on experience from gaming communities and those related to role-playing games, hence I am mainly interested in the answers related to that sphere.