I believe Gruber was inspired by how people wrote emphasis in plain text emails and other text documents. Most MUA at the time would treat trailing whitespace as a hard rather than soft line break. This is from my--now aging--memory, and I can't find a source to corroborate. I do recall, though, there were clients that didn't do it well (ahem, Outlook), and would break plain text formatting of deeply-nested quoted text. (Don't even get me started on how Outlook single-handedly changed culture from bottom posting to top posting).

> I have seen that as a feature on Android keyboards, but I would be very much surprised to find it in non-keyboard software.

It just happened to me in VS Code! Not even a Copilot thing

[a few moments later...]

It turns out to be a macOS system setting, defaulted to on, that is polluting everywhere

https://github.com/AdamMaras/vscode-overtype/issues/9#issuec...