Content is rarely removed from iNaturalist. Exceptions would be things like nude images of humans or pornography. Commercially spammy content and copyrighted images are hidden from public view.
There are so many gray areas that such a policy would have to be very detailed. If in doubt, feel free to flag the content to get a second opinion. From the FAQ:
What is considered inappropriate content?
You know it when you see it, right? Stuff that violates Section 2 of our Terms of Service is definitely inappropriate and worth flagging or otherwise notifying the admins about. Milder forms of rudeness are unfortunate, but probably not something we’ll delete." Although iNat is primarily for sharing observations of wild organisms, observations of captive animals, garden plants, and other organisms most naturalists may not find interesting are okay (they’re alive, after all). Other abiotic phenomena should be marked as “no evidence of organism” in the Data Quality Assessment section. Things that clearly have nothing to do with nature, like what someone had for lunch, are inappropriate and should be flagged. Pictures of pets, humans, abiotic phenomena, or obvious test observations are okay unless someone repeatedly posts such content. If you encounter inappropriate content, flag it or contact the site staff at help@inaturalist.org
That said, it’s probably not worth flagging observations of “what someone had for lunch” unless they continue to post that type of content despite being politely guided toward appropriate use of iNat.
See also this affiliated thread with recommendations for common scenarios: Dealing with low quality observations and inappropriate content on iNaturalist