This happens to me at work all the time. I'll think I can fix an issue faster than I can give a thorough answer about what went wrong and what it will take to fix it. Sometimes I'm right and I'll get back to them quickly to say we're testing a fix. But sometimes I'm wrong and I keep intending to say something but then repeatedly think "oh wait but I've almost found it".
It's entirely useless. Anyone who asks for an update can see it plainly on the repository. There will either be commits against the default branch, an open PR, or a branch with in-progress work.
In any other case (unclosed issue, missing changelog) the solution is to step up and help. Mention that you've replicated the issue, found the solution is up, and that the issue can be closed. Or contribute a changelog
Ideally contributors would be able to opt into automatically blocking some kinds of comments, but of course that would require a perfect "spam filter" system or manual moderation by other volunteers so that the contributor wouldn't be distracted.