Meanwhile I live in the UK and it's completely standard for monetary quantities.
I’ve seen that use for sure. Perhaps a little telling we’re talking about blockchain tech and that’s what people are using. Is it really about a fast distributed transaction log, or… is it about the money first.
The Financial Times recently changed their abbreviation for million from “m” to “mn” to help screen readers. They would typically read an m suffix as metres; I guess the FT chose mn rather than mm so that screen readers would not say millimetres instead of million.
I am American and commonly see mm to mean million.
It has to be capitalized. 1.5MM is 1.5 million. 1.5mm is 1.5 millimeters.