People have mentioned tables here, and...yeah, they're messy, but I wonder how common of a use case that is for your average WYSIWYG user?
This. And proper line breaks help a lot, too. There's a reason single line breaks are ignored.
> People have mentioned tables here, and...yeah, they're messy, ...
IIRC, the "original" markdown does not include tables. They've been added by GitHub (I think), because it made sense for them, and many parsers started to adopt. I agree they are not easily readable in "source mode". It helps to properly align stuff, though, but it's a PITA.
See
https://blog.codinghorror.com/standard-markdown-is-now-commo...
and linked previous blog posts if you (or anyone else reading this) are interested in the history.
Documents that don't hard-wrap (they could opt to hard-wrap without consequence, to your point), when viewed somewhere that doesn't make it trivial to engage soft-wrap, are much more of an issue than the tag barf mentioned earlier, IMHO.