Sorry I posted the wrong issue, it’s actually a duplicate of https://github.com/KaTeX/KaTeX/issues/3168 which was filed last August. I guess it’s not that long, but it was annoying for my use of KaTeX on https://mitchellkember.com/notes4u where I see it frequently. For example it affects \left\lvert\vec{b}\right\rvert which is a pretty simple piece of TeX I’d expect to render fine.