I care much more about revision history than I do about comments. When I'm trying to figure out code I do it in "git blame" mode - what I'm hoping for is a single, atomic commit that links back to an issue thread. Ideally that issue thread will have all of context I need to fully understand the change.

This works great in codebases that are designed to be read in that way, which is why I'm so keen on every commit combining tests, implementation, updated documentation AND a link to the associated issue thread.

I'll sometimes open an issue seconds before I make a commit, just so I can have an issue number I can associate the commit with. This is great for adding commentary later on - I might post a comment on an issue thread a year after the commit that help clarify some useful detail that, with hindsight, I should have recorded.