Board Thread:Editing Discussions/@comment-6697950-20150429190520/@comment-3250527-20150430084606

I think it was an ESL (English as Second Language) issue, since "-er" is used as in context of "one who does __", as opposed to "-or", which has its own obscure rules on replacing "-er".

Dictionary.com (elucidate) claims that "Elucidator" is the correct spelling.