I agree the current terminology isn’t particularly clear. I feel “Subscribing” is probably more suitable, but still not completely clear.
Facebook opts for a very explicit “Turn on notifications for this post” - there’s no possibility for confusion there!
Twitter opts for something very similar: “Turn on mobile notifications”
Alongside the wording, I think it’s worth considering how the ideas of “watching” and “tracking” have changed with the recent introduction of push notifications (whether through discourse-push-notifications, the mobile apps, or some other method).
I think there now needs to be some kind of distinction between what a user would want to receive a push notification for, and what they might want to receive an email for. Right now, both email and push notifications fall under the ‘watching’ label.