I get aggravated at seeing these comments too, but I'm not surprised why they don't use the 'formalized' routes for sharing. Tagging someone in the comments is the path of least resistance, and people have acclimated to it—and at this point, it's hard to change because the incentive to change would be to keep a comments section clean, which people don't really care about.<p>I'd argue that, failing convincing people that it's annoying to do so or changing to the UI to lead people to the "share" function instead, the solution is to filter these kinds of comments out programmatically, showing them only to the sender and recipient(s).