The conversation was about why the feature wasn't stable.

I have no idea how the Rust project organizes itself, but my guess is that this simply isn't a high enough priority for them, which would explain why it hasn't been made stable.

Large backlogs with stale are a common problem that software projects have.

Code reformatting is, apparently, surprisingly hard. This classic article has popped up on HN a few times over the years: https://journal.stuffwithstuff.com/2015/09/08/the-hardest-pr... (one reappearance at https://news.ycombinator.com/item?id=30566111)

So I can understand why such a feature remains behind an experimental flag. "But you are not touching code, only reformatting comments!" - well, not just thta. Adding whitespace and N+1 effectively empty lines will at some point cascade into whatever logic the wider code formatter will have to consider. The number of edge cases must be non-trivial.

I don't know if this is hard in their codebase (although I have a guess), but I have worked on a code formatter before and easy-sounding things were often an unimaginable nightmare.

I mean... check out the issue tracker for any project, open source or commercial. It's just how it goes when things aren't a priority. Happens all the time.