When using the following command in a command block on a vanilla server,

command @p{!name=player_name} arguments

"{" are used instead of square brackets for formatting issues on here.
Basically one example was when the command:

tp @a{r=10, !name=sky_wingace} x y z

was used to tp any player but me away from an area using the !(not) modifier for name. The actual affect was that it tp'd all players(even me) away from the area and to the specified x y and z coordinates in the command block.