Some examples for the MeW page on Markdown-only formatting [mew.toot.cat], to show how they look in actual practice:

Character formatting:

• bold
• italic
• strike
• underline
• [link text](URL) e.g. toot.cat - URL must include protocol://
• ^superscript -- like: E=MC²
  • I don't know how to turn it off without a space.
  • You can even do supersuperscript: Normal^superhyper makes "hyper" look like a superscript on "super" -- both higher and smaller

Lists:

• bullet item one
• bullet item two
  • sub-item for item 2 (2 spaces per indent)
• bullet item three

1. numbered list item 1
2. numbered list item 2

Fixed-pitch:

inline fixed-pitch text

multiline fixed-pitch text:
multiple lines
of fixed-pitch font
(for pasting code examples and such)

Syntax highlighting does not seem to be supported at present. (Tsk tsk.)

Text blocks:

Header 1

Header 2

Header 3

quote-indented text

Be sure to leave a blank line after the last bit of indented text, or the renderer may decide it should also be indented. (Nobody knows why.)