as an end user, I don't much care what fonts & other justification/hyphenation settings an author chooses, so long as I can override them via my device / reader app preferences!'
for me that's caecilia, fully justified, no hyphens ( I'm not that hard to please
)
the " my font appears darker" seems a non issue, as every reader has a brightness control built in ?
what bugs me about the Kindle hyphenation thing is that I cannot turn it off at device level, & I suspect I cannot turn it off by editing & then sideloading the speicfic azw file(s) either ?