I read it as it’s up to the person who opened the PR whether to apply the nits, or whether to ignore them and use the approval to merge. This is how our codebase works: you’re free to ignore minor suggestions, but if you do edit the code, reviews are dismissed and need to be provided again.

Basically, an unaddressed nit doesn’t block merging. But any code changes will require fresh reviews.

If the change is very minor, it’s very quick for someone who has already approved to check the last commit diff and reapprove.