Two days ago there was a small miiverse update. Nintendo’s Marty reports two main changes.
1. The search box for finding users has been moved up in the 3DS and the Wii U, to match the web version of Miiverse. This helps in finding users not posts.
2. Only for the Wii U and Web version of Miiverse, a filter function has been added to the Activity feed. You can select all the people you follow, or only friends.
Update/Edit: Tom from Nintendo adds, “You can now unfollow users with restricted Miiverse access from your User page. “
How? “Go to User Page > Connections > Following”