Besides HTML, we use Flash Player and Adobe Air to connect to Sling. By default, Flash encodes everything in UTF-8. I saw that https://issues.apache.org/jira/browse/SLING-559 resets the UTF-8 default of Jetty back to ISO-8859-1. Only HTML forms can set charset=UTF-8, all other posts are always encoded with ISO-8859-1.
Felix mentions in SLING-508 two problems of the current implementation that sound more like solutions to my issue ;) I thought about adding a servlet filter that sets the encoding to UTF-8. Is there a better way to encode everything with UTF-8 in Sling? Thanks, Marc