I'd like more critters to speak Common, because I've always loved the idea of actually getting along with Kenkus here, Lizardfolk there, Leonines and Loxodons down the middle and so on, and it seems a pity when you encounter these and battles are refreshingly avoided because enough other critters are, like the player, not necessarily going to fight for the sake of it, that you then can't communicate, so actions, feelings, verbals can get misunderstood and then it begins a fight anyway. Most players, unless they've managed a few extra languages. and even those might be irrelevant to what they actually meet, only speak Common, and that can limit all sorts of play, even if it's something setting a trap. Even the odd Kenku being allowed to have a voice, rather than click, Myconids being able to talk not just through telepathy. I would give most creatures the ability to speak, and certainly Celestials. Why shouldn't Blink Dogs and Pegasi and Phoenixes and Kappa etc. all speak? They have PC's intelligence at least, and there's few things more dispiriting than reading: "This being is human intelligence and can understood all you say BUT CAN'T SPEAK". In a fantasy world where just monsters render prey to stone, blast fire and lightning from the sky and 'swim' through the earth?! Is it REALLY so hard for most things to be able to speak a PC's language AS WELL as their own, which we have the fair likelihood of not understanding, and for that reason, non-PC beings choose to speak in our common little common tongue as that's all we can handle!