I highly suggest that this Follower Suggestion design be peer-reviewed.

Content recommendation systems have a huge effect on how communities grow and evolve. One thing I like about Mastodon is that user recommendations are done by humans, not machines. This go-slow approach is more resilient to algorithms (even the simple one presented here..)

Here's a recent paper that discusses how recommendation systems can reinforce bias.

https://blog.acolyer.org/2018/05/24/algorithmic-glass-ceiling-in-social-networks-the-effects-of-reco...

So before this gets unleashed on the world please do your research and study the available literature. Get experts to review it and listen to the people that have been doing this for a long time. You can then avoid repeating the mistakes of the past.