This requires pulling together several theories, but it's what I thought when I read this passage:
What if "the element" was what gives Hoid his powers (at present, we only know about functional immortality and world-hopping, but it seems quite likely that there are others)? From what I understand, Brandon has said that Hoid is not a shard, but gets his power from something else. From the snarky voice of the epigraph, it's fairly clear that whoever wrote it has made "the element" a part of themselves. Hoid, with a mysterious power source, fits that bill quite nicely, and is witty enough to enjoy the joke.
For the Lerasium argument, I have to admit I just don't see it. Our only real experience with Lerasium was with Elend, and while he became a powerful mistborn, he was still very human. The element is something powerful enough to worry someone who has been around since Adonalasium shattered, most likely someone who has held a shard since then. Ruin (Ati) certainly didn't seem very worried about Elend's power when he was confronting Vin.