as far as I can tell, makey makeys are setup so that they are already keybinded, so why enable the extension? make him popular

I think the extension might just exist to encourage Scratchers to use a Makey Makey in their project.

ok, thanks

The extension adds things like the konami code to your game without having to add advanced code.

Also, if you press and hold the SPACE key down with

when [space v] key pressed

then it will register 1 press and then after you hold it down for a few seconds then it will register about 30 per second.
If you use

\(Makey Makey\) when [space v] key pressed

then it will constantly register ~12 presses per second no matter how long you hold it down for.