Comment by paldepind2

My theory (which might be completely wrong) is that models do this because it improves quality for vibe coders.

When vibe coding the content of user prompts is ground truth and the only way any human thought affect the code base. So if the vibe coder says "do X not Y", recording int comments that "we shouldn't do Y" is important. It ensures that the agent doesn't accidentally decide to do Y tomorrow, which would frustrate the vibe coder who'd feel that the agent doesn't "remember" what it was told yesterday.

So for people who look at the code the comments are obvious and completely superfluous, but for the vibe coder it's a way to ensure that their tiny (relative to the size of the code base) input is not forgotten.