How to block LINE group posts?

I'm using the LINE web app, in fact on a desktop inside chrome.

So I am a member of a group, so as are a few dozen other people.

And every morning there's this one user who just posts "Hello."

Sure, I blocked him. But on LINE that doesn't stop his posts from getting to my terminal.

Now let's assume that every other person in the group just enjoys those posts.

So how can I stop the posts from even appearing on my terminal without leaving the group, and without bothering the person about their habit which I don't like?

Yes, I "muted" the group.