Yeah, this might be one of the worst websites I've seen. This is really unenjoyable to navigate.

The rationalisation appears to be that there are two viewports, one left, one (when expanding sidebar items) right.

The left-hand scrollbar controls and reports on the left-hand viewport. The right-hand scrollbar the right-hand viewport.

More conventional organisation (and less confusing, possibly) would be to retain the scrollbars to the right of the corresponding viewport.

Note that left-handed scrollbars are occasionally used elsewhere, as in the X11 Athena Widgets (Xaw) set:

<https://en.wikipedia.org/wiki/X_Athena_Widgets>

For a better reading experience, try the pdf: https://journalofillusion.net/index.php/joi/article/view/983...

I actually liked that they're always visible and not occluded by my thumb on mobile.

Accessibility would be too accessible. For extra fun, make the scrolls bars reversed and inverted axises. After all, it's not like there are disabled people who use assistive devices need simpler, properly-designed websites. Also, it's not GDPR compliant and demands acceptance of cookies.