> For example in my keyboard the micro sign (µ; not to be confused with the Greek small letter mu)
The greek letter mu IS the micro sign, where do you think it comes from?
The greek letter mu IS the micro sign, where do you think it comes from?
MICRO SIGN (U+00B5)[1] vs. GREEK SMALL LETTER MU (U+03BC)[2]
1: https://www.fileformat.info/info/unicode/char/00b5/index.htm
2: https://www.fileformat.info/info/unicode/char/03bc/index.htm
I’m not a font designer but I can imagine that the micro sign often appears around Latin letters whereas the Greek letter mu doesn’t, so that font designers might space them differently for that reason.
For fun I compared 10µm (upper; using the micro sign) with 10μm (lower; using the greek letter mu) in the comic sans font face. https://imgur.com/qwnnAqD
IIRC, to enable adoption. Many of the codepoints were adopted from other encoding systems, and it was often useful to support 2-way conversions without loss while Unicode was being adopted.
What's a "duplicate" is also sometimes in the eye of the beholder.