Regarding the original question, I guess that I would agree that we should post using whichever "english" we feel more comfortable with. On the other hand I would like to state that NNES do have regionalisms that end up being unique to a particular group of speakers.
I grew up in a non english-speaking country and I learned BE at school since I was 7. I have friends who were raised bilingual in half british households and we used to speak in english. On the other hand, we have so much influence from the USA that we incorporate a lot of "americanisms" into our speech. I think we ended up having this regional midatlantic english. I have heard myself saying "cheers mate" and "way to go dude" in the same conversation. On top of that we incorporated some expressions that we created just because of where we were living and because of our own culture.
Personally, now that I live in the US my english is more of a mixture. For instance I ended up saying "fuel" since nobody would understand when I said "petrol" and "gas" doesn't quite fit in my vocabulary

. The same when it comes to accents.
I guess my point is that whenever a groups of speakers, native or non native go through similar cultural experiences, they end up with some particularities in their speech that originate a regional form of the language.
Cheers
Ed