I just changed my document to polyglossia but now I get:
Writing index file tagebuch.idx
Package csquotes Info: Checking for multilingual support...
Package csquotes Info: ... found 'polyglossia' package.
Package csquotes Warning: Using preliminary 'polyglossia' interface.
(csquotes) Some of the multilingual features may not
(csquotes) work as expected.
It does not seem to do any harm but I guess it can hardly be normal to get either that or a warning to use csquotes if I remove that