> There's no discomfort at all to me if, e.g., it stored
> 32-bit counts and is indexed by the last 6 bits of the
> character.  That's a measly 256 bytes in all.

Or, for the same space, 16-bit counts indexed by the last 7 bits. Then there's no aliasing for 7-bit ASCII, which is still very common in my world ;-)  Needles over 64K characters aren't.

Which is a weird rule of thumb that's served me well, although for no solid reason I can detect:  when faced with a universe of tradeoff possibilities for which it appears impossible to get a handle on "the typical" case, optimize for _your_ cases. Then at least one user will be delighted in the end :-)