f.e. if i get bumped within the first 60 and loose a noticable amount of my life
f.e. if a thrust or overhead would have done the job but i get sideswing spammed more then once by my own teammate because he is out of control or whatever
f.e. if a cav comes fullspeed couchlancing into a group where one or more friends are still in it
f.e. my teammate ranged fellow opens my block and causes my utter destruction that way (that causes for some unconscious issues with this class to rise to the surface and makes me mad)
+
The general principle: Accidents happen, but carelessness is somebody's fault. If I'm damaged by accident (e.g. the target dies and my friend's swing follows-through) no biggie, but if I'm damaged by a teammate shooting me in the back when I'm moving predictably that's not OK.
I encourage folks to use M in most cases. Ordinarily it doesn't do much, but it can sometimes help teach really careless players a lesson.