I agree with you that these people must be punished in some way, but a couple of notes with what you propose.:
MAC ban It is impossible to apply on the internet, it only works on local networks because the MAC Address of the original sender isn't included in any of the network packet headers.
About Ban IP: The vast majority of ISPs provide dynamic IPs, a blocked IP is solved simply by restarting the router.
The problem is that sooner or later that blocked IP will be assigned to an innocent person (who has no technical knowledge) who will try to do something on itch.io and will have problems, it can even be worse, some ISPs connect several users via proxy, block one aIP, it can block dozens of innocent people.
Blocking IP is never a solution, on the contrary, it is something that simply worsens the quality of service for legitimate users.