Even at night?
Earth's shadow can be avoided even in low earth orbit:
The "can" in the phrase "An orbital data centre can be effectively in your line of sight and it can be relatively close" is doing a lot of work. It's a polar orbit, and over half the time will be over an ocean, and not over anyone at all.
At https://en.wikipedia.org/wiki/MetOp#/media/File:Ground_track... you can see the ground track for MetOp-B, in Sun-synchronous orbit at 817 km elevation, so a bit higher. It also shows the line-of-sight in the egg-shaped white outlined region.
A ground station will need to be within that region (which is large), or a satellite will need to relay via another satellite (adding more distance). In either case, the average latency will increase.
Since consumer devices don't support ground-to-orbit laser communications, there will need to be ground stations. How many are needed to get the latency low enough? Why not replace the ground stations with a compute center?
