Formatting gets messed up when I make edits

[rcdailey]

Type in some simple markdown text:

Then Markdown Here on it (so far, so good):

Then make a small edit, like hitting ENTER after the sentence at the start. Formatting gets screwed up:

The behavior differs depending on where I do this. In this example, I'm testing via on the troublefreepool.com forums. When I try this in my Fastmail compose editor, blank lines become double blank lines, so the vertical spacing gets really messed up.

Simple edits to the HTML formatted output should not cause this behavior.