(A blog post in response to a blog post. How quaint.)
"Imagined vastness" sounds like a very specific instance of the more general "sense of wonder" or sensawunda. For me I get that feeling of imagined vastness when reading Iain M Banks' Culture series.
I don't get the Stack Overflow vertigo he talks about, but I do have a feeling of holding something almost physical when I've got something on the clipboard and I haven't pasted it yet. It's similar to the feeling that I (maybe it is just me) get when I know there's a bit of coffee left at the bottom of the cup.
Atemporal hotel lobbies is something I can't really relate to. I do have my own unnamed feeling though:
Cycling to work
It's that moment when I whizz down our sloped drive and start pedalling up to the road. Because I WFH I go out at lunchtime these days, and the feeling just isn't the same as at the start of the day. It's something about the connection between foot to pedal to chain to wheel to tyre to road.