Many people have opinions or want to give feedback about Ubuntu. If they are simple bugs with a crash or display corruption, that's fine, they can file in Launchpad.
But, comments about the design or concept of the system are more problematic. They come up all over the place, such as "Some Unity feedback" in other places that are not really about Unity.
Ideally the answer will be a place where the comments
- will actually be read by the design team
- will tend to encourage people to read the existing comments and not post the same thing again and again
- perhaps will tend to bubble up good solutions rather than strange ideas
- will not be annoying to people who are trying to use that place for something else