I've noticed a lot on popular topics on Scott Alexander's ACX on substack, once comment numbers reach the high 3 digits or so, the page gets unbearably slow and

I've noticed a lot on popular topics on Scott Alexander's ACX on substack, once comment numbers reach the high 3 digits or so, the page gets unbearably slow and sometimes even crrashes my browser tab when I try and scroll or select text. I haven't bothered to try and debug what's going on - my guess would be they're bubblesorting the comments or something dumb like that - but I do know that if you turn JS off for that site, the post itself loads instantly, and shows you the whole thing at once rather than firing event handlers as you scroll down or click or select text. So +1 to substack for working fine without JS enabled (even for subscriber-only posts) but if someone from there is reading this, can you take a look at what's causing the problem in the first place?