I think it largely depends what you are trying to achieve.
If you are trying to document the actual information provider / provenance for a single element, you could use the RM feeder_audit attribute which is available to every Element.
However my reading of Nuno’s use-case is that this is much more about commenting on the interpretation of the score "Diet information provided by elderly mother - not sure this is entirely reliable’, rather than “Information provider: Vera McNicoll” (Both may be used, of course).