I said this in a similar thread, and it relates to some of the comments here about echo chambers and the like.
Allowing users to suppress virality whenever the feed is sorted by “Hot” or “Active” or “Top” by weighing the value of a post by the popularity of the community it comes from. This way, posts with a small amount of upvotes from a small community can be considered as equally “Hot” as those from bigger communities.
Ideally it’s be an option in selecting the sorting of your feed, but I think even if users only use it sometimes it will help diversify feeds here … and be something Reddit never did too AFAIU.
If meta-communities were to also arrive and be combined with this, you could end up with a really powerful set of feed controls.
EDIT: spelling (vitality -> virality)