Despite the awesome "Follow" button that was added to the top of issues, I still see a lot of people posting "subscribe" or "+1" in the issue queues. I think there are two reasons for this:
1) If you aren't logged in, you don't see the Follow button
2) It only appears at the top of the issue, but people are going to be most tempted to "subscribe" when they have read to the bottom of the thread and determined that the conversation is incomplete and they want to get updates.
The fixes I'd suggest:
1) The Follow button appears to anonymous users, but takes you to the login page.
2) The Follow button appears at both the top and bottom of the issue. The one at the bottom should be positioned above/below/inside the comment form, wherever it is most likely to catch the eye of someone about to post a quick "subscribe" comment.
3) Comment validation should include a check for basic "subscribe" posts, and the error should remind people to click the Follow button.