Currently, it is inconsistent if the profile picture is a link or not. In the main feed, the profile pictures hovering to the left of the posts are links, but the profile pictures within the posts are not links. On the notification page, profile pictures are part of the notification link itself. On the profile page, the profile picture is not a link (nor is the account name or handle, but that's a separate thing).
In general, but especially on mobile, it would be helpful for the profile picture to be something you could click.