The domain name is being converted to PunyCode (https://en.wikipedia.org/wiki/Punycode). This is a defence developed to prevent spoofing of domain names using indistinguishable characters from other character sets than ASCII. Before this was fixed by browser developers, it was possible to execute an IDN homograph attack (https://en.wikipedia.org/wiki/IDN_homograph_attack) and spoof sites using characters that looked like e.g., google.com/paypal.com when they rendered in your browser address bar, but were actually a completely different domain as far as automated systems were concerned.
Edit: typo.
Re:What one may find in robots.txt
by learnstats2 on Monday May 18, 2015 @07:46AM
(#9563848)
That's how internationalized domains work.
Wikipedia: https://en.wikipedia.org/wiki/Uniform_Resource_Locator#Inter...
Interestingly, Hacker News doesn't support this standard, and the link on the front page shows the unfriendly version.
Edit: Thanks for the links! :)