Come to think of it, a way would be if server registered when someone highlights you (and unhighlights you), that is when you point xhair at somebody, it shows you his nickname.
In this case it could work as for example:
Ashog [Defibrillator] The_Beholder
Ashog
The_Beholder
Ashog [crouch]
Ashog [uncrouch]
Ashog [crouch]
Ashog [uncrouch]
Ashog [crouch]
Ashog [uncrouch]
Ashog [unhghlight] The_Beholder
That would mean that I killed The_Beholder, stepped on him and looked at him (his nickname was shown ovem my xhair) while crouching/uncrouching (so that it's only when I am standing on his body and looking down on him that I can crouch/uncrouch w/o unhighlighting him). Mad idea of course but makes fun to fantasize :)