Off the top of my head, there are quite a few a functions that only appear in one or the other, but wouldn't make sense to be both. EG:

1. `isPrivateUse` or `isSurrogate` would make no sense in `std.ascii`
2. `isOctal` and friends wouldn't make much sense in `std.uni` either.

It would appear the only functions `std.uni` has that *could* be in `std.ascii` are `isMark` and `isNonCharacter`.

There would be no actual characters in `ascii` that would fit those descriptions, so I'm not sure about this one. Adding them would probably be useless, and break code now, rather than prevent breakage.