The M1/M2 thing is still used as a shorthand to describe aggregate cell behavior when simplicity of explanation is desirable, but is really not taken seriously anymore with regard to single cells. That is, there's a lot of evidence that while certain groups of proteins are more likely to promote inflammation and certain groups to suppress it/promote regeneration, there's too much overlap in any given cell to say that this cell is an "M1" or "M2" cell. The functional ambiguity of the microglia is fascinating, and I've been putting a lot of my effort there recently. I'm becoming more and more convinced that some regenerative therapies that our lab has developed act on the microglia as the most upstream event. That might be crackpot, on the other hand.