As others have said, there are names you'll never be able to use because they contain the whole or part of a profane word. "Kukuri" is one such example.
You also won't be able to use names that contain "suk" anywhere, so names like Tsuki, Tsukasa, Mitsuko, etc.
In chats, you'll notice that words like "reputation" is censored because it contains "puta" (Spanish/Portuguese profanity), so even profanity in other languages can be censored.
Their chat filter is just pretty extreme.