> if you want a 'visual' line-break you have to add unnatural double space at the end of preceding line.

That’s just a bad syntax choice on Gruber’s part. CommonMark adds trailing backslash as an alternative, so that will work in most places these days.

> And even this is renderer dependent, I don't think is part of the spec (?)

Yes it is. Quoting https://daringfireball.net/projects/markdown/syntax: “When you do want to insert a <br /> break tag using Markdown, you end a line with two or more spaces, then type return.”

> IIRC GitHub comments renderer does't need it

Yes, GitHub decided on a wilful violation of Markdown for issues and discussions.

> text editors which auto-convert double space into ". "

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

> > text editors which auto-convert double space into ". "

> 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...

> That’s just a bad syntax choice on Gruber’s part.

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).