This is way too simple...
You shouldn't just warn players! Disconnect the hacking player and warn others about this action!
And a Custom Script is NOT a comment!
A Custom Script is simply a Jass/vJass/cJass like in a GUI line, and what you've typed there will show an error in the World Editor when saving a map and the map won't start in Warcraft III. More precisely, when selecting the map, the player slots won't appear.
One more thing: DO NOT USE BLUE FOR Codes:! Do you see how ugly it looks? When I am looking at it, I am seeing the text twice! And it's radiating in front of my eyes!
At this stage, I cannot even rate this, because it is simply too simple.