I wonder if Miqo'te can purr

[CyrilLucifer]

Science to the rescue!

Despite many humans associating purring with cats, it's actually something a variety of mammals can do. In fact, humans can sort of emulate the sound and the process by doing what is casually called a voiceless "German trill," which is a trill of the tongue in the back of your throat, rather than the front, which is what you see in Spanish. If you don't know what it is, the easiest way to do it is to gurgle without water, without your voice attached.

I only use the human comparison because cat purring requires a similar exhale; it lets you feel the vibration giving you an idea of how it works, just know that purring takes place in the vocal chords, rather than your throat. Cats and other mammals that truly purr require specialized vocal cords and it's likely something instinctual, not learned like human speech or the songs of oscine songbirds (which, by the way, actually learn their "languages" using the same part of the brain, super neat).

I'm not sure if, with those specialized vocal cords, they would be able to make the same range of sounds as the other Spoken races. I honestly don't think SE put that much though into it.

I actually think the more cat-like Mithra would have been likely candidates for purring, the Miqos in XIV lost a lot of the more cat-like traits from XI and are more straight up catgirls. If you were to ask my opinion, I don't think they can. I agree that it's probably a very juvenile thing to do, if possible at all, since I believe that purring in itself is considered a trait for sociality and the connection between mother and infant.

tl;dr
As far as I'm aware, there actually haven't been a lot of terribly in-depth studies on the biological mechanics of purring. Even if there has been, it's a fantasy game. There's only so much you can realistically apply to it.