I have, from time to time, wished to ask for clarification from an OP, and could think of no way to ping a person. A high percentage of MSE questioners are anonymous. At my age, that seems to make little sense, but I can see that today's youngsters automatically assume an online pseudonym/username unless there is an awfully good reason otherwise.
So that is the detail I find interesting, is there now, or could there be, a method for pinging an anonymous user who is, at least, registered? For now, I mostly ask people to email me if they are interested in, say, getting a pdf of some article I already have. Sometimes they do, not many. Some newcomers hardly seem to notice such "comments," so it would be nice to be able to generate an email to them, perhaps saying only "Please check your responses/comments at question number xxxxxx."