Nothing.
It is time consuming to return the few cents of everyone who doesn't read my warning. Because of the thousands of transactions, my transfer page loads super slow. It's also harder to verify that someone actually made the transfer, because I have to scroll through a hundred newer transactions.
By default I don't return, unless I'm asked to. The time I waste would cost me more than the few cents I'll give back.
In other words: I don't want to waste time, in order to lose money, because people didn't read my warning.
// Of course, it is completely different if I have to refund bigger sums. In the east 2 weeks 1 person sent me 26 SBD and another sent 24 SBD. I refunded both pretty fast.
The first one didn't even notice that his money were missing for 2 hours until three days later.
(You can verify all of that by reading my transaction history)