While true, there’s also an asymmetry here in that a city can expand their landfill or sewer system capacity- orbital space has a fixed capacity

That's not really true. The "capacity" such as it is is defined by current technological ability to track the assets and respond to changes quickly. There's a whole ton of work to be done there as satellite operators only update their position every few days usually. It should be at least daily and ideally hourly or even by the minute.

WTF? Space is incomprehendibly big. The number of potential landfill locations are very limited.

Isn't this thread discussing a very specific orbital range? The 450k-800k range is big, but I'm not sure I'd classify it as "incomprehensibly big".

Anything orders of magnitude larger than the Pacific Ocean deserves that title IMO.

It’s at least bigger than the surface of the earth :)

Landfills can go underground though! Although I agree that it's unlike we can dig several hundred thousand kilometers :)