Insane with = (equal sign space):
= My h1

== My h2

=== My h3
Insane headers end at the first newline found. They cannot therefore contain raw newline tokens.
Equivalent sane:
\H[1][My h1]

\H[2][My h2]

\H[3][My h3]
Custom ID for cross references on insane headers:
= My h1

== My h2

=== My h3
Sane equivalent:
\H[1][My h1]{id=h1}

\H[2][My h2]{id=h2}

\H[3][My h3]{id=h3}