I totally see your point here. Of course, certificates are a questionable financial instrument on its own. If it is a good thing to be able to trade bitcoin without actually owning it is indeed doubtful...
But imo it is good news in terms of mass adoption and integration of Bitcoin in the financial market. Comdirect is a online bank owed by Commerzbank, one of the biggest banks in Germany. The more institutions accept (accept it being a commodity at least) Bitcoin the better...
Well, mass adaption may be a positive point.