I like the country flags for several reasons.
First of all, when I see an English speaking country, I can safely take the author's production as the gold standard of English. Conversely, for certain other countries, some caution, mixed with leniency, is called for.
Gold standard of English is hard to define. There's British English, American English, Australian English, New Zealand English, and various other native Englishes, all of which are not quite the same and have many local usages and turns of phrase. And then there's ESL English, which is actually the most international version. Meaning two ESL speakers often communicate better in English than two native English speakers from different countries. Which I find quite amusing, even though I understand why.
That’s basically complete and utter nonsense.
The fact is, while spoken English does have a bit of variation that’s occasionally confusing to a speaker of another dialect, it’s overwhelmingly mutually intelligible. When it comes to written English, if you standardize for spelling traits (o vs ou in words like color, -ise vs -ize, and a handful of other words), it’s almost impossible to tell the nationality of a writer. It takes a very astute reader to notice the clues.
My qualifications on this matter: I studied linguistics; my mom is a retired ESL teacher; I’m American but have lived abroad for years, regularly communicating with Brits, Aussies, and the occasional kiwi or South African, as well as with many nonnative speakers, as well as observing nonnative speakers between each other; and I worked as a technical writer (in English, for an international audience) for years.
What is true is that sometimes, two nonnative speakers will have complete understanding of an utterance, whereas a native speaker will not, if the nonnatives happen share a common misuse of English which happens to collide with native English. For example, here in Switzerland, nonnative speakers will routinely use the word “manager” to mean “executive officer”. A native speaker will instead “misunderstand” them as meaning the English meaning of the word.
ESL teachers in Japan joke that “the only people who can understand a Japanese ESL student’s English are other Japanese ESL students”.
So while
nonnative <-> nonnative can occasionally outperform
nonnative <-> native speaker communication, it will practically never exceed
native <-> native speaker communication.
If the native speakers speak two very distinct dialects, one can of course run into trouble, but nonnative speakers will have just as much trouble if it differs a lot from the dialect they learned.