Especially with Lemmy getting support for plugins soon, I don't see the need for making a new platform
A new sorting method for "unanswered" is a cool idea. I'm not sure if it's quite as simple as just finding posts with 0 comments, because people can put additional questions in the comments but it's still unanswered. Also how do you sort them for posts with the same number of comments/answers. But this is definitely something that a plugin could handle.
I saw someone else suggested we could just put "[unanswered]" in the title and then edit the title to "[answered]"