The reporting user read the documentation as suggesting that this is the "note" syntax:
NOTE Some note text here, in a codeblock.
It could be more clear that "NOTE", "WARNING" and "IMPORTANT" are not part of the code block syntax, and are separate block elements.
When trying to set a code block as a note, warning or important (as specified here) the keyword isn't parsed/recognised. For example,
warning This won't be set as a warning
Counterexample will work on the other hand:
This is a counter example