As far as I know I can see a user profile and the activity in this site. But is it possible to leave some message for a particular user? Say I want to (please read I have to) tell J.M. something about one of his very old post. I know the @ functionality to draw his attention. But for a definite way that he has looked into the post, PM functionality would be great (of course, with a possibility of abuse by requests/spam). So I am not requesting a feature, but asking what you guys do here in such a situation. Also, is there any kind of "leaving message" facility available here?
Please note J.M. can be any name :)