Re: Although...
mmccul, I think you have misread RFC 822 section 6.2.4. It says, 'This specification treats periods (".") as lexical separators.' It says that the effect of these lexical separators is to divide the name of the mailbox and turn it into a sequence of tokens.
Dividing a string in different places will yield distinct sequences. Note that the sequence ("a", "b"), which is a sequence of length 2, is a distinct sequence from the sequence ("ab"), which is a sequence of length 1.