Updated it to check new posts too.

JSFags feel free to make it better.

var op = parseInt(document.getElementsByClassName('op')[0].id.split('')[1]);window.addEventListener("load", LoadListener, false);$(document).on('new_post', LoadListener);function LoadListener() { var replies = document.getElementsByClassName('reply'); for (var i=0, r; r=replies[i]; i++){ var rid = parseInt(r.id.split('')[1]); if (rid 100000) { var body = r.getElementsByClassName('body')[0]; var elements = body.getElementsByTagName('a'); for (var j=0, a; a=elements[j]; j++){ if (a.hasAttribute('onclick')) { if (a.onclick.toString().includes('highlightReply')) { var pid = parseInt(a.href.split('/')[5].split('.')[0]); if (pid < op - 751) { if (!a.text.includes('pb')) { a.text += ' (pb)'; } } else if (pid < op) { if (!a.text.includes('lb')) { a.text += ' (lb)'; } } } } } } }}