Not sure it’s entirely silly to put code on crates.io. I’m a pragmatic and I’ve thought about writing some kind of post which says “Being on crates.io is how you vote”.
It encourages two things, A) publishing and B) being stable-compatible. In return you get a “vote” in matters of what rust code looks like and what it needs to work.
This is the pragmatic view, the strict view would say there should be no regressions at all. But we do need help to find them in the first place. This particular bug you linked, is not a regression from Rust 1.0.