At least in the editor preview, this doesn't render linebreaks:
> foo > bar > baz foo bar baz
Screenshot: 
Is this a problem of my browser? Or something else? On StackEdit it works as expected!
At least in the editor preview, this doesn't render linebreaks:
> foo > bar > baz foo bar baz
Screenshot: 
Is this a problem of my browser? Or something else? On StackEdit it works as expected!
The Linebreaks section of the Markdown help says:
End a line with two spaces to add a
<br/>linebreak
> baz > bar Which renders as:
baz
bar
This works as expected.
If you require explicit line breaks, use backslashes at the end of the line:
> foo \ > bar \ > baz foo
bar
baz
Personally, I consider this preferable to ending lines with two spaces (as in the other answer), as the latter can be easily overlooked.