Could you tell me if there are any rules regarding questions not appearing or being deleted?

Rather than being about strict rules, it’s more about whether something goes against common sense, morals, internet literacy, or the purpose of the site. There are plenty of ways to put it… Lately, we’ve been seeing a lot of posts like that being hidden. Where exactly is the line between hiding and displaying them? The staff may well be discussing that among themselves right now.

https://universe-club.jp/help/promiss/ Posts that aren’t questions, show disrespect, or constitute harassment may be deleted or hidden. In particular, regarding the purpose of a post, it states: “If the administrators determine that the content of a question is primarily an expression of the poster’s opinions, the question, along with all answers to it, will be deleted.” The specific borderline is subjective and depends on individual judgment, so it probably cannot—and will not—be clearly defined in writing. The administrators’ policies may also change.