Userscript to never see reply from someone you muted again:

// ==UserScript==
// @name         Stacker News - Remove Muted Comments
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  Remove muted comments instead of showing 'reply from someone you muted'
// @author       ekzyis
// @match        https://stacker.news/*
// @grant        none
// @run-at       document-idle
// ==/UserScript==

(function() {
    'use strict';

    function removeCollapsedComments() {
        document.querySelectorAll('div[class*="comment_collapsed"]')
            .forEach(node => {
                if (node.textContent.startsWith("reply from someone you muted")) node.remove()
            }
        )
    }

    // Run on initial page load
    removeCollapsedComments();

    // Watch for dynamically loaded content
    const observer = new MutationObserver(removeCollapsedComments);
    observer.observe(document.body, { childList: true, subtree: true });
})();