noop is a built-in command and is not an identifier. The identifier warning has nothing to do with it. Even with it enabled, you should not get a warning about noop if you didn't have $ in front of it. There should not be a $ in front of noop. You can verify this by typing the following in mIRC's edit line-
//noop echo -a test
You should not receive any kind of message or echo because noop prevents the display.
