It was already reported in bug http://issues.liferay.com/browse/SYNC-109 and marked as fixed. Just downloaded latest RC2 and tested again - it is still not working in my case:
1. In case I'm creating folder with russian symbols in Liferay Portlet - it is synced into my MacOS with questionmarks instead of symbols.
2. In case I'm creating folder with russian symbols in MacOS - Liferay Sync show me error "Cannot upload 2 files" - nothing created in Liferay Portlet