Latency wise it seems okay for llm training to put them higher than Starlink to make them last longer and avoid decelerating because of the atmosphere. And for inference, well, if the infra can be amortized over decades than it might make the inference price cheap enough to endure additional latencies.
Concerning communication, SpaceX I think already has inter-starlinks laser comms, at least a prototype.
Underwater [0] is the obvious choice for both space and cooling. Seal the thing and chuck it next to an internet backbone cable.
> More than half the world’s population lives within 120 miles of the coast. By putting datacenters underwater near coastal cities, data would have a short distance to travel
> Among the components crated up and sent to Redmond are a handful of failed servers and related cables. The researchers think this hardware will help them understand why the servers in the underwater datacenter are eight times more reliable than those on land.
[0] https://news.microsoft.com/source/features/sustainability/pr...