IME there is nothing so disliked as unasked-for advice. Plus the person you so advise is more likely than not to purposely ignore your advice, or worse, to try it on the spot and of course discover that it doesn't work for them because they're unused to doing whatever it is you're advising. They'll give you a mental finger. All of a sudden you're down several notches, going from a rider whose form is admired to an idiot.

OTOH, if you're asked for advice, absolutely give it. You'll go up several notches, from just a rider whose form is admired to a knowledgeable source of wisdom.