Start spamming far-left YouTube videos to the public channel at the same time, according to the general theory of nutball political physics the two should cancel each other out

The problem is that takes up valuable airtime. The denser the mesh the more airtime is wasted on the junk.

In MeshCore a concept of regions has been recently introduced - you can scope channels and messages to a specific geographic region (which is set on a repeater) and it will not propagate outside of the given region.

That way local channels don't need to flood the whole mesh, same as with trying to send a message to someone or reach the management interface of a repeater you know is in a given area.