For unknown reasons, I was upgraded to Sixt Diamond tier recently. I've only rented a few times in the past few years so this was surprising.

I've already vouched not to use Sixt at MCO again, but out of curiousity, would the diamond ststus give me any benefit there? There is only one counter, right? And I imagine there is no counter bypass with this tier?

I suppose the biggest benefit for me will be tier matching with another rental company, at least for US rentals. I Europe there might be actual benefits at major airports, apparently there are "diamond lounges" in Germany.