Exactly. They very explicitly stated that you can't use linden in a display name. It only stands to reason that they wouldn't want anything that could possibly be misconstrued as linden in one either. And rightly so, because for every person who does it as a goof, I'm sure there's at least one other person doing it for nefarious reasons.
By the way, Doing It For Nefarious Reasons would be a great sex group name.