Due to the language barriers you pointed out, the truth is you really can't work for anyone from anywhere in the world. Most of us can't.
Having access to potential customers anywhere in the world doesn't mean someone is able to create web pages for them all. It's like calling customer service and being routed to someone in India who does not speak American (which is our own version of English).
We have to repeat the same simple issue over and over which someone in America could straighten out in no time, yet the person on the other end of the line cannot understand the most basic conversation.

Simply being able to speak English is not enough.
Just as we might be confounded by trying to perform customer service for those in England (speaking a more proper version of English but with a slang all their own) or even Ireland (due to strong accents of their own), you may be trying to spread yourself a little too thin with those claims unless you are working with someone who is more comfortable with English.
Chances are you will run into the same issues you are having here on other people's sites as well when it comes to both main site content and things in the page such as the h1 tag.
Just something to think about.