Dark matter has not been observed directly so can not be said to conclusively exist but given our current understanding it is by far the best model for describing how the universe works. There are other theories but they do not describe reality as we observe it.

Dark matter does describe reality as we observe it we just haven’t observed dark matter itself.

A straightforward filtering system… Like tags?

I think a blanket ban would make people try and hide the fact that something is ai. Like it or not ai isn’t going away. I feel disclosure in either the title or body is the better choice. By all means ban those blatantly not adhering to the disclosure rule though.

Tags in Lemmy would be really helpful here as users could chose yo filter out all ai related posts from their feed, though a similar effect can come through requiring a keyword like “[AI]” to be in the title and a user end keyword filter.