Actually, I was the one to raise the issue earlier.
This has been sort of "discussed", though not quite, since certain users didn't see that it could be the subject of debate. The problem is that, as a matter of course, people whose country is strongly and exclusively associated with a single "national" language don't understand such problems at all, but people living in countries such as India, which counts over 400 languages, understand it very well. In the world, there are more nations, from Switzerland to Togo, China or Mauritius, that are plurilingual than nations that are monolingual, but this seems to have escaped the attention of many.

I agree that flags are nationalist symbols that do not adequately represent languages.
For instance, the flag for the English language is the British flag, although, on one hand, a number of other languages are spoken in Great Britain, so it is kind of an insult to the speakers of these other languages, especially when they are indigenous and have predated English on the island, such as Welsh, and on the other hand there are far more English speakers outside of Great Britain than inside.
I understand, though, that flags are nifty visual helpers.
Alternative visual coding systems have been proposed, although there doesn't seem to be any standardisation within sight on the web.
In any case, I think the British flag is the worst possible option to represent the English language. It should be either the red cross of Saint George alone or some other kind of symbol.
I personally support international standards, so I think the 3-letter ISO-639-3 codes should be applied.