The thing is, some times I don't think one should hit M when getting teamwounded. It depends a lot on the situation. For instance when two people hit a guy, the guy dies from one of the hits and the other hit goes into the teammate. Often people hit M for that too. Also in sieges one can't really blame people for teamwounding a bit, since one either has to rush the flag or it's a super tight area. Basically I just hit M when someone teamwounds me in battle and when it's a really unnecessary team wound, like team bump when I'm in a 1v1 with an other infantry, or the same with ranged team hit.
Anyway, the thing is if you're a bit unlucky you can do some team wounds that people really shouldn't hit M on, but some people always hit M no matter what the situation, and then 3 perhaps is a bit too little.
One thing they could add to make less team wounding, is that the one hitting a teammate gets a message too, saying something like "Opps, you hit a teammate! Be careful." Because some times it can be hard to know.