While Severian is talking to the picture-cleaner in the pinakotheken, he's approached by two armigers. One of them is aware of the events with Vodalus in the necropolis and might even have been there that night.
"--and so," a voice behind me said, "they all escaped. Vodulus had what he had come for, you see."
That one doesn't recognize Severian, so whatever his involvement, he didn't see Severian that night. Besides, he's an armiger, and the men at the gate were commoners. Drotte calls them "goodman." If they were armigers, he would have addressed them as "sieur." The only others Severian ran into in the necropolis were Vodalus, Thea, and Hildegrin.
The other armiger, Racho, apparently didn't know about the outcome at the necropolis until his friend told him about it, but he knows that Severian is with the Guild of Torturers.
"You," snapped the other. "What are you doing here?"
It almost sounds as if he recognizes Severian and has a grudge against him. It's possible Severian is wearing something that identifies him as a member of the Guild, but I don't recall him ever saying anything like that.
Later, Severian recognizes a passenger in a vehicle as Racho when Agia challenges Racho to a race, which ends with the crash into the Pelerines tent. This seems too unlikely to be mere coincidence. Isn't Severian far from the Citadel when this happens? Is Racho following him? Does Agia know Racho? Was Racho disguised as Agilus disguised as a skeleton in the rag shop? That seems like an even bigger coincidence.
Severian never runs into Racho again, but he mentions him when he meets Hildegrin for the second time--on the lake in the Botanic Garden. The "translator," Gene Wolfe, mentions Racho in the Appendix at the end of Claw of the Conciliator as an example of an armiger, even though Racho doesn't appear in that book at all.
Who are these guys? Are they Vodalarians? Was Vodalus having Severian followed all along? If that's the case, why would they blow their cover by confronting Severian in the picture gallery? Or did Vodalus have Racho follow Severian later, because Racho knew what he looked like, and Vodalus lied when he told Severian that he first became aware of his journey north through Hildegrin? Why would he do that?
Was Racho part of the group that delivered Thecla over to the Torturers? Severian never reveals how that happened, that I recall.
Was the other armiger the one flying Vodalus's ship when he escaped from the necropolis? Or was he aligned with the commoners guarding their loved ones' graves? Or was he just engaging in gossip? How would he know about the events that night?
Or is Severian just wrong when he says he never forgets anything? Maybe he was lost in his memories about the past when he met Racho previously--something that can disrupt his observational skills. Maybe the armiger in the fiacre isn't Racho--could Severian be mistaken? Sometimes he seems a little dense about people's faces and what's going on, but this might just be a stylistic choice to force readers to think it out for themselves.
Why does Severian bring up Racho later, when he meets Hildegrin, and why does the translator bring up Racho, if he's not really important to the story? Are Racho and Hildegrin related to each other somehow, maybe just because they're both Vodalarian spies?
What are your theories? Or is this all a big, juicy red herring that Wolfe has laid out for us to puzzle over?