I've found it's had unacceptable scroll performance in long contexts for a while now.

In this case, it takes me 12 seconds to see content when first opening the link, and about 18 to re-render content when scrolling.

I think that's partly because it's a fairly long conversation and partly because of all the LaTeX. There's enough formulas there to fill a small text book, and I doubt their renderer is all that efficient.