The lerfu shifts (BY1) consist of these cmavo: ga'e, ge'o, je'o, jo'o, lo'a, na'a, ru'o, se'e, to'a.
For past usage, I am searching through the corpus I have collected of 900 kilobytes of pure-Lojban text. The corpus includes all texts published at lojban.org/files/texts, many large texts from the Wiki, IRC logs, and texts from the CVS server such as Alice.
ga'e is only used correctly in algebra, to mark variables named with capital letters. The author assumed that the shift would apply across multiple lerfu strings.
to'a is never used correctly.
lapoi pelxu ku'o trajynobli contains the sentence ".itu'e ga'e ca cpedu fi do to'a". ga'e and to'a here both act as pro-sumti, which was probably not intended. Here, ga'e and to'a were probably intended to "capitalize" (emphasize) the words between them, but as lerfu modifiers they cannot modify the emphasis of words.
None of these are used anywhere in the corpus, except that the utterance "zo ru'o" appeared on IRC in response to a line of Russian text.
(update 2010 some usage, mostly bad/joking/quoted; examples follow)
10 Feb 2010 10:54:46 <kribacr> .i je'o je'a mo je'i mo je'u je'e
28 Oct 2006 02:29:01 <cizra> jo'o
30 Mar 2005 17:17:43 <rlpowell> lo'a
"30 Aug 2009 12:24:46 <bancus> ru'o ty bu".
zai has not been assigned to this section, but it has a similar function to the above cmavo. It is also not used anywhere in the corpus.
(update: usage exists, but all as zo quotes or typos for za'i)
This word is not used in the corpus, though nau was used in the algebra text where na'a was probably intended.
(update: usage follows)
ni'o na'a la djozis ze'a pei na pei jundi
Josie hasn't paid attention for a while, don't you think?
23 Jul 2010 06:02:14 <Broca> se'e pa vai xa vo gai
- Converts future letterals to uppercase. The change applies until it is shifted back with to'a or cancelled with na'a.
- Cancels all shifts (font, case, etc.) currently applied to letterals. Any shifts that occur earlier in the text do not affect letterals from this point on.
- Convert the next sequence of digits to a character code in ASCII, Unicode, or some other agreed-upon character set. The code includes all digits until the next non-digit, the end of the letteral sequence, or na'a.
- Converts future letterals to lowercase. The change applies until it is shifted back with ga'e or cancelled with na'a.
- Converts future letterals to the Greek alphabet. The change applies until it is shifted by je'o, jo'o, lo'a, or ru'o, or cancelled with na'a.
- Converts future letterals to the Hebrew alphabet. The change applies until it is shifted by ge'o, jo'o, lo'a, or ru'o, or cancelled with na'a.
- Converts future letterals to the Arabic alphabet. The change applies until it is shifted by je'o, ge'o, lo'a, or ru'o, or cancelled with na'a.
- Converts future letterals to the Lojban (Roman) alphabet. The change applies until it is shifted by je'o, jo'o, ge'o, or ru'o, or cancelled with na'a.
- Converts future letterals to the Russian (Cyrillic) alphabet. The change applies until it is shifted by je'o, jo'o, lo'a, or ge'o, or cancelled with na'a.
ga'e: uppercase shift
na'a: cancel shifts
se'e: character code
to'a: lowercase shift
ge'o: Greek shift
je'o: Hebrew shift
jo'o: Arabic shift
lo'a: Lojban shift, Roman shift
ru'o: Russian shift, Cyrillic shift
The scope of a letteral shift needs to be defined. I will elaborate on Arnt's specification in BPFK Section: lerfu Forming cmavo, also following the "Microsoft Word model" specified at Interpretive conventions for lerfu formatting cmavo.
A letteral shift lasts until another shift of the same type replaces it, or it is cancelled by na'a.
(The sole usage of ga'e assumed that it would not end at the end of a lerfu string.)
It is not so far specified where a se'e construct should end; I propose that it should be able to be terminated with na'a, because na'a terminates other sorts of shifts.
One possible interpretive convention for these cmavo (apparently intended by the founders), is that a parenthetical shift or font-and-face change that is not followed by lerfu would be taken as applying to whole words - sort of like a mark-up language. For example: "to'i ga'e toi mi to'i to'a toi klama" would be "MI klama".
Given that Lojban does not seem to be intended for holding multilingual spelling bees, and that a dictionary containing many unused cmavo with bizarre functions could confuse learners of the language, the BPFK does not recommend to include the alphabet shifts (ge'o, je'o, jo'o, lo'a, ru'o) in learning materials intended even for advanced learners. The cmavo should not be reassigned to have other meanings, however.
The clarifications made to the scope of lerfu shifts give a consistent model of how shifts should be applied, and do not invalidate any known usage.
I believe that my scope clarifications are consistent with those in BPFK Section: lerfu Forming cmavo, even though that page says otherwise.
Given the lack of usage of alphabet shifts, omitting the unused alphabet shifts from learning materials should not have any significant impact on the language.