Yeah, I wanted to still keep it a bit high, but usually exchanged amounts are smaller than that. Above that it makes much more sense to use a "real" exchange

Yes, it receives tips, and sends back in another currency. When balances reach or drop to a certain amount, I deposit or withdraw, keep it balanced.
You made Poortbot on your own without affiliation or Stake approval, so is there any chance that Stakes notice tips transactions like this increasing and ban them?
I dont see anything wrong with what you are doing, but they can think this are cases of abuse and multiple accounts.