Advanced way, mods actions are published as a filter, enacted on the client. User choose their mods, subscribe to them, their client obtain those mod action list and use them to filter the raw feed.

This way mods can "delete" things on other instances too.

In practice, every user is now a mod. You can include any user as being a moderator for you.

Very advanced way, the user's client, for a piece of content obtains all moderator actions, for each moderator automatically evaluate credibility and reputation score, weight mods action in proportion to that score, take all actions for all mods taking weight into consideration to determine "consensus action" and then apply this action to the piece of content.

There are many many other ways to do this. All of them better than current centralized abuse-prone Web 2.0 garbage