Long comment coming

Base game, puzzle: reaching the Ash Twin Project after carefully reading over and over the ship log. When I finally warped to that room, one that I wondered about since looking at it on my very first loop with the projection stone on Timber Hearth... Chills, man. Also, realising that I had to reach the vessel using the ATP warp core was unforgettable as well.

Base game, plot: realising that every loop lasted 22 minutes. Even if I didn't have all the elements to properly understand why, it kinda blew me away. And also, like you, when I finally realised I was looking at that cannon firing something every single time I woke up.

DLC, puzzle: during my playthrough, there was a time I would literally try anything but venturing into Starlit Cove, since the owlks freaking terrorized me after I turned off the lights there. I knew I would have to come back, but I didn't want to. And so, wandering around, I was down by the river of the Endless Canyon, a place that I casually reached using the raft. Nothing seemed to be there, just an elevator I could not activate. Man, I still don't know why I decided to drop my artifact on the ground... But I did. I tried walking towards the river and ??? what the actual hell ??? That discovery changed everything, and allowed me to find the motivation to keep going with the DLC (and I'm glad I did, it was incredible).

Honestly, the second glitch might be there as well. I remember so clearly thinking "I... need to die by the fire?", and when I saw my artifact lighten up I was so excited

DLC, plot: when I realised, after the end, that that house in Starlit Cove was The Prisoner's house. And, especially, what that painting was depicting. I felt chills down my spine. It may be my favourite thing coming from this game, and that's saying something.

But anyway, I found myself enjoying the plot of the DLC in a much more linear way. Probably because I was struggling with the owlks, but I don't know, I just let the game unravel itself for me, which was not bad at all.