I strongly suspect Coulson and Fury were winding Maria up, and then Clint was winding Coulson up, and then Maria, and it all gets messy and confusing and Maria has had a-god-damn-nough. (There was a rumour she started about Fury as well. And got people to believe it. But it faded out after a while/Fury put a stop to it/owned it. For some reason the Coulson/Clint one never did go away.)

To be fair though, I can actually see Clint/Coulson and don't mind it *grins*. There are few Avengers pairings that bother me. But few that I will write *hugs Clint/Natasha*.