I don't use most of the software you mention, but converting FLAC to other formats is pretty easy. E.g. with ffmpeg you'd say
ffmpeg -i somesong.flac -o somesong.mp3
or similarly for other formats. There are more options to control the output bit rates and that sort of thing.
There's an HN thread about this and yes it sounds like the guy is being stupid and/or there was a communications error. He submitted a PR for a potentially breaking change and it was closed as "needs discussion". That is, instead of clicking "open PR", he was advised to instead click "open discussion" and talk about the proposed change and its potential downstream effects. He instead got pissy and started spamming forums.
https://news.ycombinator.com/item?id=47941590