[law_of_poe]

Your observations are pretty accurate.

I'd like to add that something similar to Urban Dictionary has existed for a very long time now (10+ years): eksizosluk.com. They had their fair share of trouble with litigation but mostly managed to protect free speech. In fact it is so successful that it spawned many clones, which themselves became very popular websites.

Content is the main bottleneck. Something like UD exists because it generates its own content, whereas HN or Reddit clones don't exist because there isn't enough Turkish material on the web. A good part of population doesn't understand English, and the ones who do, choose to assimilate in the more interesting English space (ahem).