In reality, most non-native English speakers I know speak and write
English way better than an average native speaker. In reality, among all
speakers (native or non-native) there are huge variations in the level
of skill, ranging from "lolz asl?" to Pulitzer-prize winning prose. It
is *that* which the Babel templates are trying to gauge, *not* whether
someone is a native speaker or not.
The distinction is routinely made in the language translation community
however, it's not just a Wikipedia thing and it's not just an English
language thing. It's simply that it's extremely rare for a non-native
speaker to have absorbed all the culture and reflexes that inform a
native speaker. For instance, a highly-educated non-native might not
realize that he/she is using words that are too big to be appropriate
in a particular context, or ones that passed out of common usage years
ago and are now only found in books from the 1980s. Ironically, this
is orthogonal to educational level and intelligence; even less-educated
native speakers can pick out the foreigners, even though they might not
be able to articulate what cues they are noticing.
Of course, since Babel templates are self-assigned, they say as much
about ego and confidence as about actual linguistic skill.