Heading 1

Heading 2

Heading 3

Heading 4

Heading 5

Heading 6

Bold text

Text

I think SO just has a styling issue here: Heading 3 (###) is just bold text with a different font (which actually makes it appear smaller than plain bold text). Heading 2 (##) on the other hand is already much larger and has a weird over-large margin below it. Heading 1 (#) again is only a bit larger.

Suggestion: Fix margin of h2, make h3 larger. Or h2 and h1 smaller.