Thank to the loads of feedbacks it turned out that the Google bug mentioned earlier only comes up when using Firefox and you’re logged into your Google Account. When you log out or just simply copy the link from the results, it works fine, ‘cos only the JS based tracking (Personal Search) escapes it in a bad way.
More on, Matt Cutts already faced another IDN issue as he wrote it down in his blog:
Q: “Any results on why IDN Domains don’t show pagerank?”
A: I’ve seen a couple that do, but I’ll check into why most don’t. My guess is that there’s a normalization issue somewhere in the toolbar PageRank pathway.