BTC, mBTC, µBTC, satoshi - simples.
I am definitely a fan of SI units. But practicalities might mean things play out differently. For example if I scribble down the value of something as 1m
BTC with a poorly written "m" then a reader may have a hard time working out whether it means one megaBTC (1M
BTC) or one milliBTC (1m
BTC).
Merchants have a habit of dictating these things, just look at sterling pre-decimalisation. And I won't even begin to go into why "a Monkey" is £500.