808. The rules concerning legacies and the presumptions of the testator's intention, as well as the meaning ascribed to certain terms, give way to the formal or otherwise sufficient expression of such intention, given in another sense or with a view to different effects. The testator may disregard these rules in any manner that is not contrary to public order, to good morals, to any law containing a prohibition or some other applicable declaration of nullity, or that is not prejudicial to the rights of creditors and third persons.