What are some methods of storing personal notes alongside code?

When exploring a new codebase, what would be some methods of storing personal notes or annotations alongside the code? If I were the only maintainer, I might consider added an actual code comment into the code, but doing so in a team would just pollute the code and the git logs.

Ideally there might be something that is not editor-specific, but I’m open to editor-specific suggestions. I personally code in VIM 50% and JetBrains IDEs (With IdeaVIM) 50% of the time. Jetbrains has a Code Notes plugin, but unfortunately that plugin does not work with the current version of the IDE.

Example notes and annotations:

foo = get_foo(bar, boom); // Actually returns a proto-foo, not a foo
foo += 1 // Alice says this is to avoid the lochness bug
if ( !flashing ) brake_light = 1;  // Bob insists on checking flashing in new code even though that feature has been deprecated for 17 years.