One thing I disliked is black, the Python formatter, with its utterly naive rules, that treat all code the same. It required me to workaround in many places, like always using a trailing comma for any list or tuple, to keep the items on separate lines, instead of black fumbling around and putting them on the same line. It was utterly annoying. This made me very vary of "opinionated" (read: inflexible unconfigurable pieces of software) formatters. Hopefully Gleam's formatter isn't as stupid as black is.