We get a lot of questions on meta about closing or reopening specific questions. That's great -- meta is the right place to discuss these matters (and is way better than comments on the question).
We also get a lot of requests in flags to tag these questions status-completed when the goal has been reached (when the question that people wanted to reopen (or close) gets reopened (or closed)). We generally honor these requests, but it's not the best approach. Reopened (or closed) questions don't necessarily stay open (or closed), and only moderators can add or remove those tags, so using these tags for this purpose sets up a maintenance burden that only five people can handle. The status tags are intended, and used by SE, for bug reports and feature requests. Discussions usually shouldn't end in a status tag. (Matters of site policy could be an exception.)
So what should you do to indicate that the matter is resolved? Ideally, report the results in an answer and then accept it; an accepted answer is the usual signal for "no more help needed". Alternatively, you can edit the title of the post to add something like "[REOPENED]". If it changes again later, you can edit again.
Almost anybody can post an answer (and the OP always can), and many people can edit, so please prefer those methods over requests for moderator-only tags on these kinds of questions.