1. What has been put in place to avoid this kind of scenario from happening?
There is not much. But Im pretty sure mods check for that on most cases.
2. If the user got wrongfully banned, is there a chance that the ban can be reversed?
Yes. This actually already happened once. Someone got framed for plagirism and theymos found out, so he reversed the ban. Ill try to find the post and link it here for you.