For example, "nit: maybe call the function updateCreditCard instead of updateCard"
If you disagree and think your function name is better (or that the two are equally bad), then I'm happy to go along with what you've got. But maybe you didn't think of this name or maybe I've convinced you. Either it's a quick fix (and no re-review needed) or you just dismiss my comment.
Reviewing a PR with "Approval" status means that the comments are just suggestions.
Choosing "Comment" status means that the comments are optional but important enough that I want to make sure that you read them. If you come back and say "I read them but decided not to make any changes" then I'm happy to approve the PR.
Choosing "Request changes" means that the comments aren't just nits.