Thank you, Sam! Here is my minimal code
CloudDeploy[FormFunction[{"x","??????!"}-> "String",#x&]]
In the browser (I use Safari on Mac) the label "??????!" changes to \:xxxx codes. I fix this with Rasterize[], as suggested above.
In general, not being a professional programmer, I'd say that using non-English characters in Wolfram Cloud is quite confusing. I would really appreciate your insights on this subject.
