I was surprised to see no choice to report someone losing a coop game on purpose. That makes me wonder. Is it okay to do? I mean, I don’t care much since I am not very invested in Starcraft any more, let alone coop (just currently using it to get free warchest loot), but I would assume Blizzard still wants it to be a thing that people like? It may not be that many people doing it, but it is very weird. Would probably have been smart to quit immediately after seeing the other guy is Master.
It is irritating indeed that there is no option to report such, least in the Multiplayer Ladder it is confirmed against Blizzards rules to team kill or otherwise.
If you see someone that is obviously actively not trying to win from the start quit the match, they are as unlikely to try and take actions against you as you are to them and if they do actively report stuff they set up Blizzard might raise an eyebrow towards them instead for an suspicious amout of “griefers” coincidently being paired with them.