note - Geonovum/respec GitHub Wiki

Marks the contents of an element as a "Note". If the element is a 'block' element (e.g., div or p) then the Note will be generate in a block that includes a Note "header" and the contents of the element as the text of the note. If the element also has a title attribute, the content of the title will be appended to the header (e.g., "Note: This is my note").

Note that the content of the title attribute will be interpreted as HTML markup. See title attributes for details.

This class is currently valid on <aside>, <details>, <div>, <p>, and <span>.

<p class='note' title='Always rely upon native semantics'>
    Remember - if you are using the <code>role</code> attribute to say 
    that a paragraph is a button, you are probably doing it wrong!
</p>

Or an inline note:

<span class='note'>This generates an inline note.</span>