Likes of shares and shares of shares are not notifications!
I think social media folks are generally familiar with the dread of checking out somebody's profile, scrolling a while on their page, liking a funny thing the person shared, and then realizing "oh I just gave someone a little thing that lights up! I didn't mean to do that!"
That can't happen on cohost! I have a nice time checking out people's pages, because even if I don't necessarily want to follow them, sometimes I find things I like or want to share, and then it is a silent action to do either of those things!
Obviously you are on your own if you like/share that person's old posts, but I still think this is pretty nice!