A really bad idea. Now a really good answer or tip that would otherwise be on the 'regular' stackoverflow (albeit in broken English) will remain, unknown, on a 'pt.overflow.' That is one drawback. Another drawback, an English only stackoverflow helps a Portuguese speaking person to learn another language that is, now, more universal. Yet another, it fractures an otherwise more unified community. My mother tongue is S…
In the ever growing globalized world, learning english is essential and it doesn't really matter what's your native language.
I think this might increase the mixed language coding that is almost a norm in Brazil.
It's perfectly fine to write code in your language, but you're just limiting the amount of people that can read you code. You might never want a remote worker from outside your country but you can't really predict the future.
The side effect of this is less people actually attempting to learn english, resulting in tons of mixed language code that's just horrible to read, even for the people that do speak the native language.
I can't count how many times I've encountered horrible half-english half-portuguese variable/method names that are impossible to understand.
Hope I'm wrong tho.