@mitch @benjamin I'm perfectly happy with that spelling if your audience isn't unusually familiar with Arabic. The Q represents a sound that doesn't exist in English, and K is a much closer approximation than KW (the naive rendering of QU).

Equally, I think many older romanisations of Chinese are better for general use than pinyin - rendering "that sound like CH but different" as CY, CH', TJ, etc. gives an English speaker a much better chance at approximating it than Q.

In both cases, as you move to an audience that's more familiar with the language in general and your transcription system in particular, the mental effort of using a glyph to represent a sound different from its role in English decreases, and the benefit of being able to distinguish between the allophones increases. So, "Qur'an" would be more appropriate for a scholarly discussion, but I'd prefer "Koran" in a mass-market newspaper.