> I argue that the latter is preferable

I disagree vehemently. I couldn't disagree more. The text has to be readable. If you force the reader to zoom in order to read the text, your website is fundamentally broken.

Moreover, neither of these considerations apply to images: "you risk having content off-screen which cannot be focused by a keyboard" "A user is extremely unlikely to think to scroll horizontally to see the rest of a document"

"There is even great president for it with documents on the web" Typo: precedent.

> either way should never reach users

This seems practically unavoidable with images, especially screenshots for example. Device widths vary, image widths vary. There is no magical image width that fits every device width, unless the image is very narrow. Moreover, I try to avoid JavaScript altogether when possible, so I don't want custom JS image viewers all over the place.

When you brought these arguments up on Lobsters <https://lobste.rs/c/dsm1up> I said it wasn’t cut and dried but that my general feeling was of disagreeing with you. I’ve thought about it more since then, and firmed my position up: you should make sure that the presence of initial-scale=1 won’t affect anything (we agree on this point), but that if you make a mistake in this area, it’s much better to have it than not to (we disagree on this part). Of your five points:

Your first point is correct. It could be reasonable to omit initial-scale=1 during development, or have something that complains on width overflow.

Your second is unavoidable: omitting initial-scale introduces a worse failure (excessively small text).

Your third I disagree with: when overflow occurs it will almost always be obvious that you could scroll, because you’ll have text or image that runs to the inline-end edge of the viewport rather than being contained by a page margin as is universally practised.

Your fourth isn’t useful—by that argument all documents should be zoomed out until the entire thing fits on screen; but we don’t do that in general because having to manage the zoom to get a useful result is unpleasant, yet that’s what you’re advocating for.

Your fifth is irrelevant, I think entirely unrelated to initial-scale.