Fred Meyer raised a good argument about the need for a WordPress writing style guide:

Words have power: power to define new users’ impression of the seriousness of WordPress and its creators; power to alleviate users’ frustration or aggravate it; power to provide information or smugly withhold it. WordPress’s current written content sporadically disregards that power, making WordPress seem like a cheaper, more irritating, and less well-executed project than it really is.

As a non-native English user, I’d also like to echo what Zé Fontainhas wrote on the comment area:

I have nothing at all against colloquialisms (or americans, for that matter), but limiting the style to a particular subculture of a particular country makes localization (and not just translation), incredibly hard. Each of our countries’ subcultures may not be divided along the same lines, for one, and any translation always ends up being either unnatural (and hence irrelevant) or, even worse, specific to a very limited group.

Overall, I like that this discussion exists in the first place. To me this signals WordPress’s maturity.