If we want to keep it objective, one metric can already be calculated based on the user history of the submitter. The spammers profile will be full of unmerged or abandoned prs. Just based on those statistics beginners might be close to zero rating but spammers would be negative.
Unless I totally missed that people are also making new accounts of each PR.
Prs are too pad cv's or novice users wanting something and vibe coding it themselves. Jellyfin player repos see a lot these kinds of prs so unlikely to be new users
Or creating repos that will merge their PR(s).
Create lots of fake repos/prs to improve your ratio?
Stars are a really bad metric for quality/popularity but they're something here. I think some sort of impact score when combined with repo age, # contributors, etc would be pretty valuable.