No, you can use whatever you want. But at least don't oppress those who choose to use "9" to mean the quantity of 8+2. Actually, it should be a "", but "9" is tolerated and I didn't feel like having and extra "9" key somewhere for decimal. When teaching, I always make sure I do a proper "" (with a full 6-like loop) for the Tonal digit "ko".

Decimal is unnatural for humans. Finger count is irrelevant. Should we use base 20 because of our toes? If you really want to count on your fingers, base 5 is better than base 10-- you can read 55 (35 decimal) that way. Or binary, then you can hit 11111111 (255 deci) without trouble (due to finger dynamics, I find it difficult to use the ring finger). I personally use binary for finger counting, each hand representing a single Tonal digit.

I agree, it should be. However, right now, it isn't all (simply) binary underneath. It's an encoded floating-point Decimal BitCoin value at the RPC level. This creates problems for Decimal as well, since the common decimal number of 0.1 cannot be represented by floats. But that's another topic.