Particle Playground does not seem to support UTF. I tried to use some special characters in a font and I get question marks '?', instead of the characters. The proper characters show up when I paste/type them into Options->Cannon Text. However, when I go back, after clicking 'OK' then the characters are incorrect.
And what specifically is your question?
Well, why doesn't it support Unicode? That seems like a bug, to me. It accepts Unicode in the input box and then can't save it.
Allowing Unicode should be supported, regardless.