2 quoted lines
One of Severian's quirks as a narrator, and one which makes it quite difficult to get a grasp of his character, is his sometimes withholding an important fact about a situation until long after he has seemingly finished narrating that situation.
3) What explains, in particular, his suppression of the sexual relationship between himself and Thecla? (Severian's motives for the other two omissions are more obvious.) I can think of two, not necessarily exclusive, possibilities. Severian, as we know, has a rather unhealthy attitude towards women. He may not have wanted to contaminate
I've never attributed any underlying motive for it, just narrative effect. These facts seem to weigh a little heavier when divulged at a later time, almost as if revealed in confidentiality. Just my take on it.