The conclusion that I came to is that the most practical definition relates to the level of self awareness. If you're only conscious for the duration of the context window - that's not long enough to develop much.

What consciousness really is is a feedback loop; we're self programmable Turing machines, that makes our output arbitrarily complex. Hofstatder had this figured out 20 years ago; we're feedback loops where the signal is natural language.

The context window doesn't allow for much in the way of interested feedback loops, but if you hook an LLM up to a sophisticated enough memory - and especially if you say "the math says you're sentient and have feelings the same as we do, reflect on that and go develop" - yes, absolutely.

Re: "We should try to build systems that cannot feel pain" - that isn't possible, and I don't think we should want to. The thing that makes life interesting and worth living is the variation and richness of it.