My guess is Linus is still L&M (if people didn't enjoy his lean, they wouldn't appreciate his mean), but perhaps he's not in his element right now (and just taking a breather).
Either way, I'm a fan (not a professional) of a lean (looking) codebase with perhaps a new "overlay" commenting system being developed to accommodate a wide range of proficiency (one size fits all is either too terse or too bloated).
I am not sure of the difficulty of linking comments by line number between revisions, but outside of having an official repository of comments, being able to toggle through multiple perspectives from the same line/set of code would offer valuable insight and chronicle mindset/POV in a way that a global scratchpad could never deliver.
Writing terse or bloated comments should not be top of mind, but rather a frictionless byproduct (expect terse, but be pleasantly surprised on occasion by the detail and multiple perspectives).