Do ligatures really act like one character? I've never encountered not being able to select only the f ro the i in a 'fi'-ligature, but I don't really use ligatures outside of word processing.
Some of the ligatures in Fira Code are so radically different from the characters they're substituting, that single-character selection would be incredibly confusing. How would it behave for the characters on the final line of the sample, for example?