I wouldn't call using 1% of the mass of Mercury to create enough living area for a quintillion people and using most of the energy our Sun produces anyway to be analogous to anything you're alluding to on Earth thus far.
But the point here isn't to dive into the moral issues. It's not even to ask what MOST civilizations would do. It's simply to ask would ALL civilizations restrain themselves this way? If the answer is "no" then we'll find at least one. Saying no civilization would engage in this kind of growth when it looks entirely possible seems like far more of a stretch than the scenario I outlined.
- the only way that alien life could be intelligent is if they exploit the resources of their solar system maximally.
Don't we have enough evidence yet that maximal exploitation of resources is a Very Bad Idea?