And since my editor strips newlines on save (and no, I will not turn that feature off), I guess I can't use it.
Oh well.
It kind of scares me that I might inadvertently strip the newlines out of someone else's markdown that I'm editing, though.
There were some systems back in the DOS/early UNIX era which had significant EOL whitespace. Spaces at the end of a line are still significant following a "\" in shell files. Some early word processors under DOS had significant whitespace at EOL, but tended to display something like a paragraph mark when it mattered.
Python had tab/space trouble at beginnings of lines, but the compiler was finally fixed so that it emits an error if tabs and spaces are mixed in a way which makes indentation visually ambiguous. That was a neat solution to the problem.
Leading tabs in makefiles were a mistake. The author of "make" once wrote that he put that in, and then, the next day, realized it was a bad idea. But he already had a user base of three users and didn't want to change it and break their code.
I thought this idea was dead and buried. Sometimes, they come back.
It would make multiple repeated BRs difficult, though, but you probably shouldn't be doing that anyways.
Intriguing: significant white space on the right-hand side. At least you can see the significant whitespace in Python.
I also have my editor configured to strip trailing whitespace but also to highlight it. People can be very sloppy leaving (insignificant) whitspace lying around in code.