Sometimes while posting in international boards, many members get into the habit of posting in English, as a result of which they cannot write good posts in the local language even if they want to. So they also want to post in English on local boards, which many local members find difficult to understand because English is not their main language. But I do not agree with the statement that posting in English on the local board will upset the local members and disrespect the local board.
There is no way one can speak and write English (as a second language) better than the native language.
It will definitely upset local people. Imagine you are a French and write in English in Français board. That's the disrespect of your own language. Imagine, you are a German and post in English in German board, isn't it disrespect of your own language when you live in a country where official language is German and everyone speaks it in that country?
The situation is different if we talk about Swiss board. In Switzerland, there are four official languages: German, French, Italian, and Romansh. If you are from the western part of Switzerland and speak French and post in French language, then that can't be considered as disrespect and will be tolerated by everyone, I guess.
I said what seemed right from my point of view. Now I never thought that local members might be disrespected for posting in English. I agree that local board members should post in local language, because it will be easier for all members to understand the post there.
Now even if someone feels comfortable posting in English on a local board, your statement implies that he should be forced to post in the local language in the local language! However, since I don't post on my local boards, so don't worry too much about this. But still just giving my opinion.