forgot to mention, the user above was unbanned. So if op was banned unjustfully, keep spamming them (ignore them telling that even your blizz account will get baanned unless you stop spamming) until they unban you.
Another people reported being banned for using multiple instances (although most users that run multiple don't get banned, it's a rare occasion)
I asked them whether using multiple instances is allowed and got this answer:
https://imgur.com/QEDO3xz.pngAfter their reply, I explained to them that said process (using process explorer) doesn't involve 3rd party, it just closes a handle. I even asked them if using virtual machine for multi instances was allowed, since there is absolutely no 3rd party program involved and their reply was pretty much the same:
https://imgur.com/6EU7CEK.pngWhich pretty much means blizzard game masters themselves dont know if it's allowed. Meaning your account depends on what some random blizzard employee decides to do with it after he sees that the handle is closed in the game.