paragraph-separate

paragraph-separate is a variable defined in `paragraphs.el'.
Its value is

"[ 	]*$"

• This variable is safe as a file local variable if its value
  satisfies the predicate `stringp'.

Documentation:
Regexp for beginning of a line that separates paragraphs.
If you change this, you may have to change `paragraph-start' also.

This is matched against the text at the left margin, which is not necessarily
the beginning of the line, so it should not use "^" as an anchor. This
ensures that the paragraph functions will work equally within a region of
text indented by a margin setting.

You can customize this variable.