@UltimateUnknown
Technically speaking the word habitable means capable of being inhabited. Thus if human technology allows humans to live somewhere. Then that place is indeed habitable. You are confusing the word habitable with hospitable. Which means a good place to live. Humans don't need a place to be good to live there. All they need is to be able to keep themselves alive, and it doesn't matter if it is happening naturally, or humans are making it possible through their own technology. You don't have a point.
As for Neptune that is exactly where people colonizing the planet Neptune would live. The density of those gases increase as you go deeper into the planet towards its solid surface. At a certain depth in a space suit you would in fact become buoyant. You would indeed float, and never fall all the way down to the surface. It would be like just laying on top of a pool of water. It would even be possible to make entire cities that would float at what to us would be a depth with a comfortable pressure. They are called Aerostat colonies if you are genuinely interested.
Oh and if you are going to argue that it wouldn't be practicable to do so don't even bother. The planet furnishes what life needs a abundance of in abundant quantities. The atmosphere is rich in the basic ingredients that a self contained colony would need to sustain a biosphere. The planet is rich in Carbon, Nitrogen, Oxygen, Hydrogen, and Water. Beyond that trace elements would be present as well. The planets temperature isn't even a major hurdle, because the planets winds would be a energy bonanza. Unlike the Earth they are nearly constant so they could turn wind turbines forever.
Imagination don't leave how without it.







