Yes, I agree - and I forgot that in C, "char" on its own can be signed or unsigned. If I pass -unsigned-char to vbcc, then char is unsigned by default, as it should be, and my string code isn't trying to sign-extend all the time.

One thing I used my "sgn" modifier for is making my right-shift instruction copy the msb instead of shifting in zeroes - avoiding the need for both "lsr" and "asr" instructions - maybe something worth applying to your "ror" instruction?

Also the sig modifier might be useful for "sub" as well as "cmp" - assuming sub modifies the flags?

I still use 1960's computing ideas, no flags just Link/Carry bit. Branches test a register for a + - or zero.
I have no CMP instruction, but have adx,sbx ( add index , subtract index ) that does not affect the carry bit.
I my case adding a real flag register, and a CMP is more pain than it is worth.