My heretical thought regarding Severian1, the Severian whose life was not intervened in by time-travellers (or less so than our Severian) is: did he exist? Severian says he did (IV ch. 38), but Severian is wrong about a lot of things. Of particular relevance to this point, he's wrong about Apu-Punchau being Sev1, which is the only claimed "sighting" of Sev1 in the book, as far as I know. One of the reasons Severian gives for believing in Sev1 is that the undine rescued him, but in Urth we find out that that wasn't because of Sev1. Similarly, the other reason, that the Autarch smiled at Severian in the House Azure, could be explained by the backwards-living Hierodules. What other evidence is there for Sev1's existence?
--Adam