There's this https://www.windowsphoneinfo.com/threads/why-does-resizing-m... (made confusing by the next person talking about Paint 3D, a different application) and this https://learn.microsoft.com/en-us/answers/questions/3991946/... (made confusing by the person being an artist and talking in peanut butter metaphors).

There's some suggestion there that shapes (including lines) are separate entities from pixels. Wikipedia references a now-deleted answers.microsoft.com version of the first question https://web.archive.org/web/20250203164656/https://answers.m... with a couple of people saying that resize is useless. Wiki also says "re-copied" images blur, which is why I wondered if that meant pasting. Also this: https://learn.microsoft.com/en-us/answers/questions/5673783/... a complaint that the tool for drawing pixels doesn't indicate exactly which pixel it will draw to.