On our site we have the celestial-mechanics tag, which has 37 questions. We also have at least a few more questions beyond that that are also about celestial mechanics but have not been tagged.
I think it is clear that sometimes celestial mechanics is on topic here, at least when it is directly relevant to planning space missions or other space exploration topics (such as near-earth object detection and avoidance).
What is less clear and has always invoked controversy is whether celestial mechanics in general (when it does not directly relate to planning space missions) is on topic. This discussion was triggered by the recent re-closure of the following question:
To prevent eternal open/close wars over old questions and to provide clear guidance to askers going forward, we need to make a firm determination as to what kinds of celestial mechanics questions are on topic. If you provide reasoning in your answer, please do not refer to what is on/off topic on other sites or what better expertise other sites may have. These factors may impact where a user chooses to ask a question but should not impact the discussion of topicality on our site.
So what kinds of celestial mechanics questions should we allow here?
As this is a controversial topic, I think we should set a high threshold of at least 7 upvotes and a score of no less than 5 for the answer that will be accepted as community policy. This can be up for discussion in the comments under this question, but I do think some kind of threshold is needed.
If the community decision results in old questions remaining/becoming closed, those questions also need to be locked as having historical significance.
Update: The accepted answer is the new community policy based on it being the first to reach the threshold.