That would be done on submission of the post, it's not something that would be done during template creation, as it would not be possible to do so. You can only alert a user to a post once it's actually been submitted - a post template isn't a "real" post, if that makes sense
I figured out the reason. I was using the account that I was mentioning. It was being used as a global template saying to contact @ name for info. So admins could use the same template. Only it doesn't work when you mention yourself. IS this by design?