If you were taught on a typewriter, you double space for life. It's impossible to stop once ingrained.

OK that doesn't show here (Firefox on Linux), I actually copied the text into an editor, and searched for double spaces, and none were found.
Tried another Browser Falkon which uses QtWebEngine, and there are no doublespaces there either.
So apparently some browsers render Lemmy posts differently.

I really wish it would come back in style. I hate the single space after a full stop, it feels inadequate.

Huh, I thought Markdown basically just ignored all extra whitespace