It seems like you build off the comments of issues, parsing for the :+1:, you could functionally provide the same tooling, but in the same additive way that waffle.io does.
We're not parsing GitHub comments ATM. That's a good idea though, but it would be difficult to track content. Maybe it's just simpler to track issues in one place and improvements in another?
Looking at Waffle.io, it seems to me that they don't actually store any data on their end. Everything is managed with issues, comments, and tagging.