>> It leaves um, uh, er and elongated versions (ummmm, uhhhhh) alone.

Something's already gone wrong here. Uh and er refer to the same sound. Uh is the American spelling. Er is British; to them a following "r" like that is just a kind of vowel.

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chrismorgan 2 hours ago | parent [-]

Um… no. Quite different vowel sounds.

(Also, in case it wasn’t clear: I was quoting from the start of the article in that sentence.)

	▲	thaumasiotes an hour ago \| parent [-]
		They're quite different vowel sounds in the same sense that "back" and "back" use "quite different vowel sounds" when pronounced by American vs British speakers. But not in any other sense. > in case it wasn’t clear: I was quoting from the start of the article in that sentence. You don't seem to be quoting from the article at all, actually. You've combined two different sentences in a way that grossly misrepresents what the article says. But that's not really relevant to the point here.