John Woldemar Cowan, The Complete Lojban Language — Chapter 17 - As Easy As A-B-C? The Lojban Letteral System And Its… (1997)
“ Why is “lau” necessary at all? Why not just use a “bu”-marked word and announce that it is always to be interpreted as a punctuation mark? Primarily to avoid ambiguity. The “bu” mechanism is extremely open-ended, and it is easy for Lojban users to make up “bu” words without bothering to explain what they mean. Using the “lau” cmavo flags at least the most important of such nonce lerfu words as having a special function: punctuation. (Exactly the same argument applies to the use of “zai” to signal an alphabet shift or “ce'a” to signal a font shift.) ”
