By coincidence I picked up House of Suns the same week you recommended it on your channel, and now having finished it I would say it's my second favorite Reynolds book after The Prefect. I thought the ending on the planet and Hesperus' sacrifice was really poignant. I initially thought the game subplot was a bit awkward too, but it makes more sense if you see it as artificial memory of the genocide against the first machine people. Abigail's memory of the boy's ghost soldiers dying to a spell represented the accidental virus unleashed on the machine people by the lines of the commonality, and Abigail's memory was implanted as a way of discouraging future decisions like that without revealing the truth of what they had done.
The reveal that the Andromeda galaxy had been veiled by the machines as a way of concealing wormhole FTL travel was a conceptually interesting way of getting around the paradoxes that arise from having something being able to travel somewhere before it could observe itself there. What I found implausible was the idea that the Commonality themselves could have wormhole weapons that spit out the energy of distant suns, and not have the ability to rig up a system of FTL communication with mini wormholes, and therefore have uploaded minds that could span the galaxy.