I mean, come on. Srsly guise. "Nakama" is not a magical moonspeak word with connotations so cosmic it CANNOT BE TRANSLATED
No language can truly be translated into another, as they aren't simply the same word using different sounds. Whenever you attempt to do so you are always inventing or deleting information. It is up the convention and the translator however to determine what information must be inferred and which can safely be expunged.
I only said nakama to differentiate from allies, I didn't think "comrade" or "friend" would make my comparison clear. Get over it dudes.
I think comrade would probably be a fairly safe translation, but not friend, as it is way too vague, Coby is clearly a friend, but is not a 'nakama'.
I think that sometimes words with fairly similar analogs do get venerated when they ought not have been (for instance keikaku). But this is a thread with One Piece enthusiasts, who likely know the meaning of 'nakama'. To use the word is to eliminate potential misunderstandings with similar vague concepts. To completely avoid it is to question the understanding of the listener (reader). Choosing which words to use should be based on who you are communicating with.
Besides, what's so wrong with adopting a new word into English, especially one that already is fairly well understood, and serves a purpose in differentiating between types of relationships. When someone says 'samurai' would you stop them and say 'actually, Japanese isn't some magical language, you should just use the word warrior instead'.