This would enable best bet recommendations for book and article titles that have a subtitle.

At the moment tags for best bets have limitations on the types of characters that can he used i.e. letters, numbers or any of the following symbols (-_ .&/'@#). Colons (:) cannot be used. It would be very helpful to be able to use colons because of how common they are in titles. Our zero result usage stats show that our users are searching article titles that include a colon.