I've tried a few programs...

* pandoc uses "Microsoft Stupid-Quotes" and turns quotes and
apostrophes into multiple garbage characters.

* markdown2 does not support Reddit's feature where a "\" at the end
of a line forces a hard line break.

After some experimentation, I settled on "apostrophe". It's a
relatively lightweight gui markdown editor, with some nice options.

* it has a "split-screen" option that allows editing the raw text,
whilst previewing final output in real time.

* it allows a choice of 5 different markdown flavours, one of which
(github-flavoured) implements "\" at end-of-line as hard line break.
It's not a 100% perfect match, but it's "good enough".

* it has a "dark mode" option; easier on my eyes.

--
Walter Dnes <waltdnes@???>
There are 2 types of people in this world
1) Those who can extrapolate from incomplete data