As the title states, I think it would be a good idea for users to be able to watch or subscribe to prefixes so they get an alert when someone uses a prefix they are watching or subscribed to.
A lot of our users are requesting this, after we merged subforums into single entities and used prefixes instead. It's nice but people complain that they receive too many email notifications, they'd like to receive notifications only for prefixes that pertain to their interests. Gladly willing to pay for an addon that offers that feature.
So if you subscribe to a popular tag you get 50 notifications per day? If you subscribe to 4 or 5 tags it is 200 notifications ??
I don't really see the point in subscribing to something that will produce so much content on a daily basis. In any case, you won't read everything.
It is the same to follow a forum.
For people that watch forums, this, in essence reduces notifications because instead of being alerted for all content of a forum, now, you are only alerted for the prefixes you are subscribed to. This is a very reasonable suggestion.
As soon as a forum receives more than 20 or 30 messages per day I do not see much point in following it, receiving 20 or 30 notifications is useless in this case as much to go and see the forum itself.
Regarding the prefixes yes it can reduce the number of notifications but from about twenty per day it is no longer of interest either, you might as well go to the forum concerned and sort by prefix.
In addition, other notifications will be drowned in tag notifications and the entire system will be useless.