We're using the word "glow" to mean different things.

Glow as in self-lit is simply using a shader that doesn't require light to produce a non-black color. That is possible a million ways, but the easiest and most straightforward is to use the ambient parameter.

Glow of the air around a self-lit region is postwork here, as millighost pointed out. It's not a trick - it's a filter in Photoshop.

The probe light node does not emit light. It generates a pattern of lighting as if there was a world around it. The nature of that world is controlled via a bunch of parameters. People who use the probe light node to make a self-lit material are like people using a car to crush ice by driving over it. Yes driving over ice with a car does crush it, but you do not need to go get your car to crush some ice. There are simpler ways.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)