To reduce the visibility of content from a specific federated instance in Lemmy, you could implement a weighting system for content in the user’s feed. This would allow the user to specify that they want to see less content from a specific instance, while still allowing them to see some content from that instance.

To implement this feature, you would need to:

1. Add a weighting option in the user settings for instances
2. Store the weight for each instance for each user in the database
3. Modify the feed-generating code to apply the weight to posts from that instance for that user. For example, if a user has set a weight of 50% for an instance, only half of the posts from that instance would appear in their feed.

This would allow users to control the visibility of content from specific instances in their feed without completely blocking it.