I like to think I would take any comments from anyone pretty seriously, it must be a significant point if they are:
a pilot
sufficiently concerned to actually seek out someone and say something
With that in mind, I like to think I would take any suggestions into account although it hasn't happened yet. I haven't (unfortunately) been busy enough to have one going solo and me having something else to do to take me away from watching them! Seems like any extra set of eyes on your student must be a good thing, as long as they don't try to be the instructor without talking to me first.