This is a very good analysis of the Thecla problem, and I want to throw out some ideas.
<in the antechamber believes there is a lady present when Severian is <there,
Back to Dan'l's suggestion about the holographic nature of Severian's acquisition of the Autarch and Thecla. Is the information projected outside of the body in a similar fashion to the way Father Inire's mirror's work, is Wolfe talking about the pseudoscience, of quantum holography or something like that? Did it even exist then? Is Thecla's projection related to the reinstantiation/resurrection of Severian and the Triskele and Malrubius, because those three for specifically created by data using powerful A.I. This is a question about Wolfe not souls. Unless Wolfe tells us a soul is present does he leave us a way in the text to tell even if he has not, and after everyone's thoughts I don't think he has, especially considering TBOTSS, worked out a definite relationship between mind, body, and soul.
//the Cumaen (sp?) knows there is another entity present at their ritual, Thecla takes control of Severian to confront the Autarch, etc.
Do the witches preform magic? Can anyone, even Severian with the post facto white fountain explanation, be said to preform magic? The same is true of Typhon's hypnotism or the duel with the shaman. This is an important point because it blurs the lines between what seem to be easy genre distinctions, scifi, and fantasy. I don't know if there is any magic in TBOTNS. It obviously exists in the later series, but this is something which I can't decide. Is Wolfe reiterating Clarkes law, especially with the heirodoles, are technology and magic for Wolfe, the same at a certain level of complexity/incomphrensibility?
//Later on,
//Severian will say that the Claw brought Thecla back. At one point
The claw is a red herring. I mean Severian finds the bush with the thorns and Wolfe suggests he is the conduit for the miracles and later in Urth it is the proximity of the white fountain.
//Though there is no direct evidence for this, note that the Thecla-in-Severian references cease in the last part of UotNS, and I like to think the reason why is that when Tzadkiel gives Severian his Reward -- a night sleeping with a woman he never sees, but knows is Thecla -- Tzadkiel has taken Thecla out of Severian and given her another body,
I have never thought of that; that is an interesting reading. What about Severian's admission that Thecla is a what a selfish and foolish woman. I don't know if he still loves her very much at the end of TBOTNS. He seems to have lost everyone, and it could be argued the personae of the Autarchs contain and limit her. Is there anymore evidence of this?
//Speech is breath is spirit.
This calls to mind lots of nasty philosophy of math, the language of thought theory, of grammatology, and wave functions. I won't talk about it if no one wants me to. Severian and Able both give metaphors that creation is an infinite set of finite modes (like the alephs in set theory), which basically means there is no language to describe reality, only a an infinite set of more accurate languages. It also means reality is continuous and not chaotic in some situations. I understand the metaphor of the logos, but I don't think Wolfe is equating it with language. I do not know if he is equating it with communication, possibly, but it's obvious he believes god "talks" to us, but I don't know if he would call it communication. In the same way whenever Wolfe treats people like data, I don't know how much he wants us to think about souls. Im his work, I think this distinction, even if cannot be made, is the essence of the A.I. debate. His opinion might change. It is perfectly possible he disguises or presents the soul as information in TBOTNS then changes it to an informational singularity in TBOTLS. It feels like this shift happens to me, but it can also be correlated to the more explicit Catholicism of the later Sun novels.
EOT;