Interesting find. I would also prefer blanklines to be retained in the roundtrip.
Just a random observation: Not all Markdown-oriented editors are equally strict about blank lines as paragraph separators. Some, like Obsidian or NotePlan (to mention two examples where I recently observed it), actually treat single newlines as the default.
And having just checked, I can confirm that even renderers like Marked 2 can be configured to work with it. In the preferences pane, go to ‘Processor’ tab and look for the checkbox under ‘Rendering’ labeled ‘Retain line breaks in paragraphs’. If that’s checked, single newlines will be treated as paragraph breakpoints. Not ideal, but maybe it can tie you over for now? On closer inspection, that last part turns out to be incorrect. It just keeps \n-separated lines together in the same paragraph. Nothing to see here.