- 90% of the time when you self-review your own PR, you're going to spot a bug or some incorrect assumption you made along the way. Or you'll see an opportunity to clean things up / make it better.
- Self-reviewing and annotating your reasons/thought process gives much more context to the actual reviewer, who likely only has a surface level understanding of what you're trying to do.
- It also signals to your team that you've taken the time to check your assumptions and verify you're solving the problem you say you are in the PR description.
Self-review is very, very helpful.
It's rubber ducking.
You could argue this is what commits are for, but given how people use GitHub and PRs, it gives some extra visibility.
And if you're going to use AI to assist you when writing the code I would argue this self-review step is 100% mandatory.
Adding context to both your commits and your code review tools pull requests / merge requests makes everyone's lives better. Including future you, who inevitably is looking at the PR or commit in the future due to an incident caused by said change.
I have been following this personal rule for well over a decade, and have never regretted it.
A nice side effect is that going through a self review and adding comments to the PR has helped me catch innumerable things that my coworkers never had to call me on.