BuyFromEU

In theory it sounds good, in practice I think it might not work so well. The problem with moderation was already mentioned. How do you stop people from posting shit in other languages, especially smaller ones that most moderators won't know? Sure, they can use translation tools, but those aren't perfect. I see the danger of either moderating too much (mistranslated posts) or too little.

On another note, using a common language also has a unifying aspect. Even if I can't buy a local French product in a store in Germany, it's still cool to read about it. Maybe it'll even spark a discussion about similar products in other EU countries. Either way, sharing progress like "We have a locally produced alternative for this chocolate bar now in Finland" is uplifting news for others, too.

Anyway, I get where you're coming from but I see more advantages sticking to English as a common language.