Voyager

Lemmy uses Markdown for formatting, like bold, italic, ~~strikethrough~~, code and lots of other stuff.
One quirk is that you need to append two spaces after a line to get a line break or use two newlines for new paragraphs.

This is a Markdown thing, which is what Lemmy uses for its comments.

You can see what's supported in the Lemmy docs for Markdown.

Something I didn't notice in the docs is a trick that markdown allows:
Adding two spaces at the end of the line lets you make a new line instead of a new paragraph.
Dunno who came up with that, but it generally works wherever Markdown is accepted.