163: Blank line missing after expandable-section heading

The characters +++ or + + at the start and end of a block mark it as expandable-section heading. +++ is for sections, while + + is for subsections, otherwise they are the same and collectively referred to as sections here.

The expandable-section heading is expected to be followed by a blank line, but in your case it is not.

Solution

Make sure there is a blank line between expandable-section heading and the following paragraph.

+++ Little Red Riding Hood +++

Once upon a time …

Unlike expandable-section headings, which can be used to toggle their associated sections visible and hidden, regular section-headings can have a subline that is directly placed below the heading. If you are fine with the section being always visible, consider using a regular section heading marked by --- or - - respectively:

--- Little Red Cap ---
as told by Brothers Grimm

Once upon a time …

If you did not mean to use a section heading, but want to have literal plus signs at the start of a paragraph, you can prepend them with a backslash, for example: \+++