Has there yet been any Word of God on firearms in the Methods of Rationality? I know that the other Word of God has the famous quote, "In a fight between a Muggle with a shotgun and a wizard with a wand, the Muggle will win." I'm curious if this sort of thing still holds for MoR.

Hogwarts, being a school, wouldn't have narrative need to involve any guns directly. Fights between bullies and students rarely end with gunshots even in the real world afterall. But the mere existence of such objects casts ripples on everything else. Just like modern warfare is dominated by the existence of nuclear weapons even when not deployed, guns remaining effective would dominate the shape of all wizard conflicts. Home invasions go from safe for the better wizards to potentially lethal any time. Public takeover (as in Deathly Hallows) becomes impossible. Support from demihuman races become pointless if open battlefields are impossible. Hell, all the death eaters in total seem almost comically weak against a single battalion of trained soldiers loaned from a friendly country and supported by a wizard or two. Death Eaters might be an effective terrorist organization, but could not be the army of a ruling party.

I expect that the story will remain centered on ideological and political differences, with combat remaining non-lethal. But still, knowing that you can pull off an assassination at literally zero risk to yourself at any time (Invisibility Cloak + Sniper Rifle + Portkey + Time Turner) has to do something to an actor's willingness to compromise with rivals.