Yeah this is awful. Every codebase becomes a graveyard of references to ideas or behaviors that were barely considered. It's probably also a compounding source of context poisoning when a minority of the comments/documentation are about how the current code actually works.
It also likes to spew references to documents that are not, and never have been, in the repo. So if you're not careful you'l have comments all over your codebase saying things like: foo() - Perform foo action as documented in PRIVATE_INTERNAL.doc