From AmtWiki

LeifErikson1968stamp.jpg Leif07192004.jpg
Famous Leifs, Erickson and Garret.

This is probably not the same as other misspellings, as the proper name, going back to the vikings, was spelled Leif, not Lief.

However, the most famous person in amtgard whose name is prounced like those green things on trees apparently spells it Lief. So in a sense, he spelled it wrong, though of course anyone can spell their own name any way they wish.