And surely the 12 or 13% who voted for parties other than CDU/CSU, SPD, FDP or Greens did not want either red-green or black-yellow.

The will of the people is truly unclear, and this is fairly represented in the results. Now it's up to the people's elected representatives to figure out the mess. That's representative democracy.

Two other thoughts about this situation as it now stands:

1. Such a divided parliament is very dangerous in a system in which sizable numbers of seats belong to parties opposed to the very system of government.  This is, of course, what happened to Germany in the early 1930s, and to Italy in the 1920s.  But, despite all the blather about die Linke not being a democratic party, that's simply not the case today. The NPD got nowhere near the 5% needed to take their seats.

2. My attitude toward the German result is very American, in that our system of government, with its checks and balances, is more or less designed not to run smoothly and efficiently for the majority of the moment.  Over the years I've come to value that aspect of the U.S. system. Of course, that's not the case now, with the Republicans in control of the White House, both Houses of Congress, and the federal courts, a situation which makes me long for divided government. There are worse things than a period of governmental stasis.