[Russ]

I understand your point about someone at management level but why would you be like that with a peer? Do you not think it's meant to be a sign of friendliness? If someone came back at me with "I'm not your mate" then the instant reply from me would be along the lines of "No, looks like you probably never will be, either".

IMO there's nothing wrong in trying to make the workplace a little less formal where appropriate.