Considering the Profile “landing” page is slated to become the Summary soon and this is somewhat edge case, probably not worth worrying about it much.
Typically, unless a Notifications link is specifically clicked I land on Profile Activity.
If I go to Profile (Activity) and click Notifications, there is a “Mark all as Read” button.
But if I go to User Card -> Avatar -> Profile (Activity) and click Notifications, the button is not there until I do a page reload.
On imgur they were saying it sometimes appears and sometimes does not – very likely a bug of some kind.
I thought @sam removed the Mark all as read button a while back…I can’t find that button at all here on Meta.
I could see it if I visited my notifications before visiting this topic. If I go back now it is gone…
Vanishing buttons and disabled buttons seem to consistently cause confusion for no gain, we should probably change this
I support leaving it there for notifications since this has come up a few times already.