Hi,
Thank you for the in-depth critique, I can see where you're coming from. As you could tell from the overly long footnote you're referencing, I really didn't feel I had sufficiently argued that point, and I knew it when I wrote it. That argument should have been a separate article.
You seem to be making two separate points: 1) coherence is useful for personal success, and 2) language, or something like it, may be useful as an intra-subjective tool of communication. It's best to discuss these separately.
1) Coherence can be taken in two ways: implicit, and explicit. For example, if I learn to avoid a hot stove by touching it, the next 3 times I see it, I will avoid it again. That is internally coherent, yet requires no formalization on my part. It is the structure of learning that automatically moves me in a way that simply works, and which probably helps with survival.
Explicit coherence, on the other hand, requires that I invent symbols. These need not be words, they may merely be thoughts of a tiger or an apple. I then think through the consequences of my interactions with these common identifiers, and I manipulate them to ensure they... hmm. What exactly is entailed in coherence? Is it to make sure I don't take an action that is somehow inconsistent with my goals? That would be accomplished by basic learning as well, as we saw with the stove. If it's about predicting the future consequences and checking them against my goals, I agreed in the post that we all automatically perform simple (one-step) versions of inference I called "reasoning", which many people just call "thinking". Coherence, however, requires a bit more effort.
The effort of maintaining coherence may be worth it if it helps me achieve my goals. However, within my own mind, I find I frequently vacillate about a given topic because I am constantly learning new things, as I live in an unknown and chaotic world. I never have perfect information, and I have to make do with the limited amount I get, while making quick associations based on one or two examples. I may learn in one context that A leads to B, and in another context that A does not lead to B. If I am unable to explicitly discover why there's a difference, since I wasn't able to explore it enough, I have no choice but to simply follow my gut in each new instance I see A; whether my gut tells me it's B or not B. Coherence, in these cases would not benefit me; it'll force me to ignore my gut.
Imagine a person who thinks they are kind and accepting, and because they want to maintain a coherent self-image, they get into an elevator with someone their gut tells them is dangerous. They may not be able to explain or justify why their gut was telling them to run away, and thus maintaining explicit coherence could hurt them. The problem with coherence then is that it is too restrictive (or prescriptive) when I need to be flexible. The world is far too unpredictable to fit it into simple, coherent models with static, well-defined entities. In such cases I might not bother with the extra effort.
The only remaining reason I can think of, therefore, to put in the effort to be coherent is due to collaboration of some kind - the desire to establish common terms with others and ensure they don't change. Once this process has been kicked off, by the way, it can be continued internally without needing others to be present (as you implied). In the same way we plan for actions, we can plan for hypothetical conversations, such as when we talk to ourselves while alone, or how toddlers engaged in solitary play will imitate their parents' admonishments (e.g. they'll say "don't touch that, Caleb" to themselves). There may be cases I haven't covered where coherence leads to personal benefits, so please let me know.
2) As for the intra-subjective tool, this probably depends on the fundamental architecture you start with. I do actually believe that the mind is an amalgam of many motives with only a tenuous sense of unity. In that case, the establishment of a common messaging protocol may develop with or without my conscious effort. (I equate conscious effort with something being explicit. What binds those together is the fact that they are addressing an underlying tension and creating explicit thoughts as their solutions.)
So the question of whether there is a private language between different selves can be split into whether there is an explicit or an implicit one. You probably mean an explicit one, in which case it would be motivated via failures of self-understanding. In that case... I may agree. I admit I had not considered that until this point; namely the idea that internal disorder or confusion may motivate the creation of a self-language (assuming I've understood you correctly). The properties of this language are still an open question. I'll admit you've given me cause to reconsider. If I've misunderstood you, please clarify.
I highly appreciate you taking the time to discuss what I've written. I've half a mind to turn this comment into two new blog posts, one for each topic. The second one I'll have to think about more. As an aside, I also appreciate you used the word "tension" - it shows you really understood a core piece of what I wrote. Tensions and how they arise are a critical aspect of every part of the mind, yet I find it difficult to write about them in generally accessible language; I dearly wish I could. I've even been avoiding using "tension" since I didn't think anyone would grasp it, so I've used "problem" instead.
As a final note, I hope you write something new as well. Even your comment gave me reason to pause, and that doesn't happen a lot.