I agree with you that things that are public can be linked to and people should expect that other people will link to them in order to comment upon them.

On the other hand, I think we should consider what behavior the site wants to habitualize for users. And, given that there are plenty of users who use the site for more personal stuff they don't particularly want publicized, I don't know if that should be the default affordance. Maybe if it were a check where you had to enable the link?