If you look at the CLASS column in TASM80.TAB, you will see that IN0 and OUT0 are class 2 instructions. Class 2 instructions aren't available on the z80 processors found in TI calculators, so adding them would probably just cause confusion with people wondering why they don't work. Although it would be nice if they were and we could use such class 2 instructions as TST and MLT, unfortunately we can't.

Thanks much for the suggestions, I'll implement font and a javascript option for left justifying or center justifying. The other ones I have to try.