Not exactly accessibility features, but a more general usability, even for people without disabilities. I personally noticed the lack of a scrollbar when I wanted to check how far through the article I am, but another common use case for those is to actually scroll through the document (particularly for skimming of larger documents, for which mouse wheel, space bar, or Page Down key are too slow, or in more rare situations when they are not easily available).

Unfortunately tinkering with visual presentation tends to conflict with the principle of least surprise, user settings, or even basic functionality.

The push-to-left doesn't matter. Most people will read one thing on the site so they're not navigating between pages anyway, most of the remainder aren't clicking through pages fast enough to even notice the jump, most of those that do notice it know how scrollbars work, and the remainder is you :)

I guarantee nobody will complain about the jump, but they will (did) complain about disabling basic browser functionality.

If the jump really bothers you, you can replace your rule with

    html {
        overflow-y: scroll
    }

which should force scrollbars to appear on every page whether they're needed or not. But you don't need it.

The scrollbar-gutter[1] CSS property might be appropriate to avoid this behavior.

[1] https://developer.mozilla.org/en-US/docs/Web/CSS/scrollbar-g...