In my own personal opinion, I refer to him as "Ren". Now, I know this has been mentioned multiple times, but again: the Japanese tend to put their last name first, and their first name last, even when introducing themselves. For instance, in episode 3 of the series Mermaid Melody, the sensei introduces the new student as "Toin Rina-san", when her name is (first name first, last name last) Rina Toin. The Japanese have their name order reversed for introductions and some other situations so as to not be familiar with just anybody right away. It's like saying "I'm Miss Rivers" instead of "I'm Janet" if your name was Janet Rivers. It's done so that you don't seem like you're being instantly intimate with people; note that this isn't meant to put yourself higher up than them or to appear unfriendly. Now, as for Ren's name meaning: if we were to translate "Lie" into English and "Ren" into English, using their origins, we'd get "Argent Lotus Blossom". All in all, I'd say that the "Lie" part is actually his last name, whereas "Ren" is his first name. Besides, when Nora called him "Ren!" when the Death Stalker threw him against the wall in Players and Pieces, it showed intimacy between the two (since they have been shown to be friends...although I think they may be in-between the relationship of friendship and the relationship of romance. I don't know yet). It also seems to imply that "Ren" is his first name; it wouldn't make sense if Nora called him "Ren" and it was his last name...you don't really see people doing that with their friends, right? Just trying to help here, and inserting my own opinion.