Complaints can be valuable user feedback. I'm sure the developers can see past the negativity and know that they can't make everyone happy. They can still use it to pick up ideas or prioritize what to do next etc. without taking it personally.
Yeah, they probably get a lot of requests and crazy mails, but that's part of the process even in professional development. At least in open source they're free to do what they want at any time, compared to professional work where they might be required to follow crazy ideas even if they don't want to.