I actually found the problem. It wasn't with JS as I thought, but with the CSS. I added class to make a CSS transition to fade in some elements. For anonymous users these elements had display: none;
and probably never ran the opacity transition.
The strange thing is that the transitions was on exactly two elements. So why would this only crash on long threads with 100+ comments?
So the bottom line is: -webkit-transition crashed the page on mobile safari.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…