The apis exists to perform moderation via a separate application, so in theory automated content moderation is possible, but most servers are relatively small and funding limited. This means there is little motivation to develop or adopt automated moderation.
The primary mechanism of moderation if by excluding people who break rules. Someone on your server breaks a rule, you ban them. They move somewhere else, they break your rules there and the mods over there don't care, so you exclude that instance from your server. (Defederate)
It's a simple but pretty effective system.
I think a kind of spider style bot that can be used to flag instances with high levels of rule breaking to suggest ban lists might be effective, but all automoderation comes with some level of error and we should be wary.