Sales: Prevent an invoice from being reversed multiple times

I just reversed a bunch of very old sales for 2 customers, to get them off the accounts receivable list. Then I went to settle returns and credits, only to find that there were more reversals than sales. I had to reverse the reversals, so I could square-up the accounts, because it wouldn't even let me delete the duplicates.

It makes no sense to be able to reverse a sale multiple times. Please put a stop to this!