doccords: lib/deco remove informal comment
:> any line longer than 60 characters is probably too long.
:> uppercase or non-ascii letters are strongly discouraged.
:>
-:> informal comments (lines with {:>}) should be used only for
-:> meta-discussion *about* the code.
-:>
:> whenever possible, use formal decorations. {:>} decorates
:> the next expression; {:<} decorates the previous one.
:>
