I was thinking about this post.
and I thought being able to leave a comment on a user profile would be a nice solution. Once in a while I have a question for a specific person. Once I notice a person doing OSdev and wanted to know about his projects he was working on. I remember a person mentioning a paper he did and I wanted to ask him more. I'm sure he didn;t notice my comment because he has many replies (which get commented on) and isn't on the site for days at a time. If he decided to look at his profile comments I am sure he would have a higher chance of noticing it.
I would like comments on user profiles. I dont think flamewars would be an issue and would be hard to follow if you cant reply back on the same page (you either cant post on your own profile and if you can the other person would be notified of the comment which may slow it down)