Probably misidentified as spam; filtering isn't really based on content, but at various times we've used third party tools to deal with abuse and have been constantly improving and bringing those in-house. If you email support with the details they can address it.

The biggest footgun I remember was some religious content (Christ on the cross, specifically) being identified as bad by some of these tools and filtered, which we obviously prioritized correcting.

No UGC site really has this solved 100%. Look at Twitter today with the porn reply bots. Facebook has 3-4 orders of magnitude more employees dedicated to filtering content than we have in our entire company. Automation ("AI" plus multiple signals) is the solution, but it's a hard problem.