When I spot an issue during the code review for a pull request (PR) on Azure DevOps, I can leave a comment (actually, a new comment thread).
Resolution of all comments can be configured as a prerequisite for completing the PR. Thus, setting a comment (thread) to Resolved is not an insignificant action.
How can I find out who set a given comment thread to Resolved?
Some context: Once a PR has gathered some 50 or more comment threads, it gets cumbersome for reviewers to always sift through all comments anew on every review round. The only meaningful way to tell which comments are already resolved satisfactorily that Azure DevOps appears to supply is the distinction between active and closed comments. But sometimes, developers set comments to "Resolved" themselves instead of leaving this to the commenter, at which point it gets quite confusing to find out whether the solution for a closed comment was actually checked by the reviewer already.
I dislike my own answer, but AFAIK it is the answer to this question.
Currently it's not possible to determine who resolved a PR comment.
After digging through the API I can see comments have a "publishedDate" and also a "lastUpdatedDate", as well as a "status", which for example has a possible state of "fixed". However, I cannot find anywhere that says who did it. Furthermore, there is a MS Developer Community thread about this which unfortunately is closed and can no longer be voted on. Perhaps a new one can be started to see if it gets more traction this time.
Side Note: Perhaps a takeaway of this is that one should only use "Approve with suggestions" if they're OK with the suggestions being ignored. If that wouldn't be acceptable, then one should block the PR.