Board Thread:Consensus Track/@comment-34115-20150626063702/@comment-1207741-20150627000532

My use of hair and fuinjutsu are to demonstrate that, like clan, they lack a rigid relationship to the Uzumaki and on a sentence structure-level need not be capitalized. You can say, "Uzumaki's hair," in the same way you can say, "Uzumaki's clan," "clan of Uzumaki," or even only, "the Uzumaki". If "clan" were truly part of the name you could end up with the following awkward but technically accurate sentence: "Naruto is from a clan called the Uzumaki Clan."

I'm resistant to your explanation of proper nouns because I think you're being too free with extending capitalization privileges to terms. Most grammar guides will recommend being conservative with capitalization, especially when there's a question about it. This is why I keep harping on about common usage; if clan/family were indisputably proper nouns, you wouldn't be able to find so many examples of them not being capitalized. Not everybody has perfect grammar, true, but neither do so many people have bad grammar, either.