What would you like to do?

See the 'Output' code section. I tried to use <.pre> tags or markdown indentation, but no dice ... every other line gets italicized for some reason. It'd be cool if there was a code type "Plain Text" which didn't highlight anything.

You can use the Markdown equivalent of a quote by starting the first line with a > and ending with a double line break. No need to use the code boxes.

Do these also use monospace?
+---------+
| testing |-+
+---------+ |
'---------+

like so?

+---------+
| testing |-+
+---------+ |
  '---------+

What are the coloring rules being used if no code-type is specified?

No monospace in blockquotes. I believe the code boxes default to C-like which supports things like Java, C++, etc.