Even if english speaking, it is still ambiguous. For example in my keyboard the micro sign (µ; not to be confused with the Greek small letter mu) is easy to type (AltGr + M). I bet this is the same for the majority of HN users. The US keyboard doesn’t use third level shift (usually AltGr) so most people that use US keyboard exclusively are unaware of this. Whenever I see people using the Latin small letter U (u) instead of the micro sign, all I think about is how restrictive the US keyboard actually is, and how much of a shame it is that the culture which predominantly uses this restrictive keyboard design came to be the dominant when designing computer interfaces.