From a technical perspective: Ignoring leaves the loop open. I don't know: - if you ignore it on purpose - or if you don't want to solve it or - or if you don't have time or - or if you just missed it ...
That's when I would re-send the message or do something else. A Win-Win would be sending a small "won't-fix" or whatever.
Often that's what you want! Maybe I don't want to reject your bug report outright, maybe I'll get around to it in a few weeks or months or years. Or not, I dunno.
I've had my own issues and bugfix PRs on small projects ignored, that's fine. Nobody should ever have the expectation of a response on that kind of project.
Ignoring: for the maintainer: open loop or maybe hidden closed loop (e.g. afraid of confrontation); for the requester: open loop.
The intention of saying no is a closed loop.
> Nobody should ever have the expectation...
Yes, but that's not a pragmatic solution. People sometimes DO have the expectation.