I just realized we don't need to forbid the use of colons in titles; unlike the subpage "/", the only time colons are used as a special character are with the limited number of namespaces.
Thus instead of the ":" being a reserved character anywhere in a title, only "user:", "talk:", "wikipedia:" etc. need to be reserved. Any other uses of colons should be fine. This will let us have entries for books with standard formatting of the subtitle (e.g., "The Muggles: A Tale of Woe") or other natural uses of the colon.
-TC