I'm not an advocate of showboating either. Showboating is embarrassing.
I am coming from the perspective of being a sufficiently experienced musician with enough skills to be able to teach others.
Having a superior skill to others and "showing" it does not equate to showboating. Having those abilities and showing someone with an unchecked ego of where they stand and what they should strive for is not "showboating" either.
I don't mean rub it in their face.
Let the music speak for itself, in a more subtle way
By the same token, the inexperienced player should have a good learning attitude and be open-minded about receiving guidance (especially if they asked for it). The kind of people who think they have nothing to learn (when they clearly do) are the ones I am referring to giving a "reality check".
More applicable to young children than adults, if I hadn't pointed that out.