Malbim: The palate tastes food. This is a metaphor for reasons for Mitzvos. Also they were not written. Rather, they were handed over to think about and investigate them. Also they are divided between Ishim and Bnei Adam (commoners). The great Ishim understand true matters in reasons for Mitzvos, e.g. matters of the Nefesh and its tie to Elokim, Divine clinging and putting His Ru'ach on those who guard His Mitzvos. All Mitzvos, according to their secrets, received truths are hidden in them regarding the order of the worlds, their Tikun, connection, the secret of the Nefesh and its tie to the general existence, bringing Elokus down, Atzeilus, influence, connection of supreme lights, and their ascent and descent via the Mitzvos. All of these are truths that Sechel can ponder covertly. The palate hints to this. It is speech more internal than the tongue, mouth and lips; it is more hidden than all of them.

Malbim: There are reasons for every Mitzvah that can be explained to commoners. All [Mitzvos] come to distance evil, injustice, bad Midos and foreign Emunos, like it says in Moreh ha'Nevuchim. Lips refer to revealed speech; here it is revealed reasons, to make evil repulsive and distance it.