This script can be run on the https://hn.tigran.io/post/xxxxxxx page to add Hide buttons to all main comments in the screen. I can hide them by clicking the 'Hide' button to lessen the noise after I read any root comment.

HideCommentsButtonForTigranHNWebsite.js

// works on https://hn.tigran.io/post/xxxxxxx page

let parentComments = document.querySelector('main > div').querySelectorAll(':scope > div');

function createHideItem() {
    let span = document.createElement('span');
    span.textContent = 'Hide';

    span.addEventListener('click', x => {
        console.log(x);
        x.target.parentNode.parentNode.style.display = 'none';
    });

    return span;
}

parentComments.forEach(x => {
    x.firstChild.appendChild(createHideItem());
});