I want to quickly sum up my last three posts to give my opinion on [q]. We already know that it doesn’t often occur in labels, but does so in the main text. We also know that it occurs almost always at the start of a word and before [o].
I think what I have seen from the last few posts is that words beginning with [q] have two particular relationships. The first is that a word starting [q] must have a valid counterpart word starting [o], and it is not enough for the plain word without either [q] or [o] to exist. Conversely, even if the [o] form exists, that does not mean that the [q] form will.
This suggests that, whatever the meanings of [q] and [o] are, they are separate characters. A plain word such as [kaiin] has [o] added to it to form [okaiin], and then [q] added to form [qokaiin]. The prefix [qo] is not valid.
Second, the character which comes immediately after [q] and [o] conditions the relative frequencies of these two prefixes. So a word starting [ch] will have low levels of both, whereas a word starting [t] will have relatively high levels of both. The words [chy] and [tchy] have very different patterns of the two prefixes.
If we believe that characters stand for sounds then it is hard to see how [q] and [o] can be grammatical. Words should not belong to grammatical categories according to their initial sounds (though there are exceptions). The alternative is that the process of adding [q] and [o] is phonological.
It occurs to me that the first characters of plain words most likely to take [o] are [k, t, l, r]. These are the same characters which are most consistent in acting as ‘strong’ characters at the start of words. They also show positive attraction to appearing after words ending [o]. We have already seen this from another angle with regard to [o] forms after words ending with ‘strong’ characters.
However, the problem is that the further addition of [q] makes little sense. It only seems to occur frequently on those plain words which begin [k, t]. As the sequence [y.o] is actually quite acceptable in the language, it cannot be added just to prevent a weak–weak combination. (It turns out that only strong–strong combinations are discouraged.) Though the lack of [q] words in labels suggests that the preceding word provides an environment for its occurrence.
The value of [q] must be also connected with the identity of the gallows characters, yet words starting [lk] and [cth] have relatively low [q] form frequency ([ckh] seems to be higher).
It seems as though [q] is being used to create a phonological sequence which is preferred for some unknown reason.