It isn't a "democracy", votes have a different weight based on the past participation on the specific community sub.
Some type of social credit system with power at the local and global level. Give active and creditable participants in a single community more authority there by giving more votes. Global credibility (you play nice in other communities) additionally is factored into the users ability to influence. Make this credit consumable. This way a community that wants to disrupt another will have to overspend and leave themselves vulnerable to destruction. MAD in essence.
I wonder why can't one just pick mods for themselves. E.g. "subscribe" to a mod, meaning whatever that mod hides, you don't see. It could even be mutual.
That’s exactly how it works. Default mods are just that, default.