allout-use-hanging-indents is a variable defined in `allout.el'.
Its value is

  • Automatically becomes buffer-local when set.
  • This variable is safe as a file local variable if its value
    satisfies the predicate `booleanp'.

If non-nil, topic body text auto-indent defaults to indent of the header.
Ie, it is indented to be just past the header prefix. This is
relevant mostly for use with `indented-text-mode', or other situations
where auto-fill occurs.

You can customize this variable.