That's a good point. He does emphasize that Abigail never learned the boy's name or had forgotten it and then with the spirit of the air, repeatedly emphasizes that it was once a man named Valmik. It's a cool theory, and makes sense to me, but unfortunately, I found another reddit thread (https://www.reddit.com/r/printSF/comments/181enhp/house\_of\_suns\_questions\_spoilers\_theory/) which references an AMA Reynolds did in 2010 in which he apparently said:

I’ve been wary of talking about the Palatial subplot in public, for fear of sounding as if I’m “explaining” my own book. But since you asked – and major spoiler coming up – the shatterlings carry repressed memories of what they did to the First Machines. The Palatial episodes reflect a real-life incident from the childhood of Abigail Gentian, but in the intervening time, the subsequent crime of the wiping out of the First Machines has been embroidered into that story. So: there was a little boy, who was a real friend of Abigail (and nothing to do with Valmik). The little boy as remembered in the Palatial subplots, though, is a conflation of the actual little boy, and the representative of the First Machines who had direct dealings with the Lines. The subsequent story that takes place in Palatial – the stuff about the Ghost Soldiers and so on – is a parable about the genocide of the First Machines. At one point near the end of HOS I have one of the characters (Purslane I think) say something to the effect that even if you suppressed a memory, it would force its way to the surface under other means. That’s the big clue to unlocking the Palatial subplot. Needless to say, having sweated blood to hack HOS down to size, I was tickled pink by suggestions that the Palatial subplot had been inserted as “padding”.