One of my favorite small linters I made on a previous team: // todo 2022-06-09 something ^ on that date, it'd fail the linter, and print the comment. Every TODO needed a date. Got a failure and need to get past it for now? No problem: bump the date for a week or something. Now at least two people are aware that it exists (author+reviewer)... and one is in the git history for that line. Makes it rather easy to trace b…
isn't tracking date and username provided by git (blame)?
As for author: yes definitely. And it's a great fallback option. But it's not visible in most code review UIs, and even when it is it tends to be the most recent editor, not the author. Git's CLI makes the full history of a line pretty easy to read with -L (usually, depending on if it detects a move or not), but have you ever tried to do that on GitHub? Back through several versions? It's a freaking nightmare, and nobody will try to do that while reading a diff.