Horizontal ruler:\\
{{{----}}}

gives you:
----

\\

Paragraphs are delimitted by a blank line.
{{{ This is Paragraph 1

This is Paragraph 2
}}}

This is Paragraph 1

This is Paragraph 2

----

Forced Line Break: \\
{{{This is first line,\\this is second line!}}}

gives you:

This is first line,\\this is second line!