@Paul_B one of us is missing the point here, or missing something, and I really don't know if it's you or me.
Are you getting notifications for this topic against your profile? As in are you getting a little number against your avatar in the top right of the page indicating there are notifications for you? And when you look more closely you see there are 2 notifications for this message, one because I mentioned you and one because there's a new comment (this one)? That's how someone knows.
I'll test this in a moment for you...