I don't know if this helps any (not at all familiar with debuggers), but in "load.php" the debugger in IE11 says "Object doesn't support property or method 'startsWith'" for the following statement:
$(function(){var hideDelay=0;var trigDelay=250;var hideTimer=null;var ajax=null;var currentPosition={left:'0px',top:'0px'};var container=$('<div id="itemHoverContainer">'+'<div id="itemHoverContent"></div>'+'</div>');$('body').append(container);var $mouseoverTargets=$('span.ih a');var isItemCategory=document.title.
startsWith('Category:')&&document.title.includes('Equipment - Project 1999 Wiki')&&!document.title.includes('Worshiper Equipment');if(isItemCategory){$mouseoverTargets=$ mouseoverTargets.add('.mw-content-ltr a');}