> > My idea would be to use a XML document, since we can then have special characters in the help with no problem (כהבתאס), and easily add extra tags for new languages.

> My idea would be XIF to save space.

I prefer to keep the base document in a text/XML format, as that's 'easy' to edit, and easier to parse for VB people.
But this would only be the 'master' document, we could write convertors which create a more space-efficient XIF-format and/or others, for specific editors.