On both GitHub and GitLab, users can create review threads for lines in a patch and other things. These threads have a resolve functionality. On both sites, resolving these threads can only be done by project write access/developer access, or the original author of the pull/merge request.

It is feasible for us to allow reviewers or committers to resolve threads with a command, such as when the original author doesn't choose to resolve when it is answered.

https://docs.github.com/en/graphql/reference/mutations#resolvereviewthread
https://docs.github.com/en/graphql/reference/mutations#unresolvereviewthread
https://docs.gitlab.com/api/discussions/#resolve-a-merge-request-thread