Tino, the linked discussion is just great! I am very happy that somebody opened the topic before. I basically agree with everything you wrote there. I also think that abstract classes would be stronger tool to have... But they seems to be ton of work and hiding a class in your hierarchy should not be so hard. So I would be happy to have just this why we are waiting for abstract classes.
There is no statement why this might be a bad thing in the linked discussion. Opinions vary on usefullness (some calling it "aestetics") but I believe that for framework authors this would be helpfull. And also, I believe this is an artificial restriction that should be removed for the language to make more sense.