It works for English, but sadly the selected fonts don't always have all the national characters. Sometimes there are similar enough replacements (e.g. Charis instead of Charter) but not always.
I agree, since I build multi-lingual web sites. I hope this will be helpful.
There is a little box at the top that allows you to replace the default text with the text of your choice to test whether your specific non-ASCII characters will work.
It works for English, but sadly the selected fonts don't always have all the national characters. Sometimes there are similar enough replacements (e.g. Charis instead of Charter) but not always.