User blog comment:Xilinoc/Ch. 612 - DIRTY/@comment-1268838-20150122214800/@comment-1268838-20150123015536

I was all right with that, since the entire arm -> ar thing did not translate well from Japanese to English anyway. Translation is about interpretation, and his decision to just get the idea across rather than translate things literally was a valid one.

Romanization is another thing entirely, though. There are no ifs, ands, or buts about how Yhwach's name is spelled, regardless of how it is pronounced.