But are they if you don’t even know that they exist? Once muted a person is not there anymore. This is social media, not real life. 

 You can usually still see them interacting. Hard to forget them, when you see their reactions, zaps, reposts, etc.

And they mutes leak, occasionally. 

 How can I see them interacting? I don’t see anyone that I’ve muted interacting. Please give me an example.

That mutes leak occasionally might be true. Haven’t experienced it yet. 

 People you've muted probably stop trying to interact with you. So, there's nothing to see. 

 That's a downside to posting things to the internet. Even the people you don't want to access it, can.