At present, the default setting for Other in a data-driven category to is no. If you forget about it, or if a new user is unaware of it, then it can be confusing and frustrating. I suggest that the default be yes. It's easier to see that it's on and perhaps turn it off, than it is to remember that it's off by default and remember to turn it on.
Agreed.
Will be default in 5.1.16.