What about commiting those comments directly into source files as comments with some tag? Like `// REVIEW looks like a bug`?
Actually I think that lots of things that's currently located outside of the repo should be in the repo. Like issues: just put them into some `issues` directory with some standard format and build UI around it.
That's basically what Fossil does. You get to do distributed issue tracking and wiki using it, it also has some advantages when it comes to subprojects compared to git submodules.
I like that idea and have tried that approach. Unfortunately, there needs to be tooling that can more easily parse a repository for those and make them part of the flow. Simply grepping isn't really a great way to do that.
Actually I think that lots of things that's currently located outside of the repo should be in the repo. Like issues: just put them into some `issues` directory with some standard format and build UI around it.