I've been providing feedback on documents (RFCs, RFPs, Incident Reports, Proposals, Code Reviews/PRs, etc) for a long time. I've been doing it so long that I remember doing it with notes in the margin and sticky notes attached to the relevant pages. For the last 10+ years, of course, the comments have been in MS Word/Google Docs and Codeflow/Phab/GitHub. Generally, there's no question who owns the document being reviewed. Who owns those comments however, is less clear.
The way I see it, a comment starts a new virtual collaborative document. Like any other document, the person who created it "owns" it. That person owns the content and is responsible for driving the resolution any issues raised. And like with any other document, that doesn't mean the owner does the work. It could be the person who produced the work being commented on needs to do something, It could be a mentioned third party. It could be that the comment just brings awareness and nothing needs to be done. Regardless of what ends up happening, the author owns the "document". And that means only the author can close the document.
Clear ownership is important to our success. If everyone is responsible then no one is responsible. At Uber the idea of "being an owner" is a thing, and for a long time ownership meant grabbing things and holding on to them. And when there are problems languishing without owners that's a good thing. But, like anything else, it can be taken too far. And that's something I want to push back on, particularly in this area.
Recently I've seen an uptick in comments getting closed by someone other than the person opening it. That's bad for a bunch of reasons. First, it's not very respectful. When you answer someone's question it's not up to you to decide if the question has been answered, and closing a comment abruptly ends the conversation. Second, the discussion helps others understand the situation. They could learn from it, recognize similar situations, or take it one step further and solve bigger issues. Finally, You prevent others from seeing the comment/response. If you leave it out there for others to see you might save yourself from having to answer the same question multiple times.
So, unless the "owner" has left the company, or you've reached out and asked them and gotten no response, don't close someone else's comments.