I might be wrong for sure. Don’t people expect everyone in the community to be right all the time? Or maybe it’s expected to not say anything unless there is a strong evidence backing claims. If this is so, natural conversations would be too difficult, but I can take this as granted.
I don’t however see how the technical arguments work here. Backward compatibility was not a big concern yet, it breaks constantly for new versions of GHC. It was not a big concern when introducing a significantly more severe change “simplified subsumption” (that was made opt-in, not opt-out after that), and the story of backward compatibility is known to be controversial. If it’s the dot itself, this could be overcome by chosing a different syntax. I don’t mean it should have been so, the dot itself is valuable. But I don’t see how this is a so big problem. So I don’t find this specific case somehow different in the technical terms, and this makes me looking for other reasons. But maybe I’m not an attentive reader who interpreted that epic discussion on GitHub wrongly.