Personally, I try to merge PRs as often as possible. I aim to keep my open PR count at 0.
If a PR is not quite right (which is often the case), I will clone their fork locally, and edit their commit(s) using git rebase and then merge it.
That way the user is still acknowledged as a contributor on GitHub (and they can see both of our names/profile pictures next to the commit message). Then I make a comment explaining why I edited their commit(s) on the pull request itself or the issue page. That keeps everyone happy and encourages further contribution.
It's not always practical to do this though but it feels natural in many cases.
Comments
Personally, I try to merge PRs as often as possible. I aim to keep my open PR count at 0.
If a PR is not quite right (which is often the case), I will clone their fork locally, and edit their commit(s) using git rebase and then merge it.
That way the user is still acknowledged as a contributor on GitHub (and they can see both of our names/profile pictures next to the commit message). Then I make a comment explaining why I edited their commit(s) on the pull request itself or the issue page. That keeps everyone happy and encourages further contribution.
It's not always practical to do this though but it feels natural in many cases.