KB) We should avoid having a "commons" if we are to avoid tragedy. (KBSure -- the air in my lungs and in my scuba tank is excludable, so it's no longer part of the atmospheric commons when I appropriate it. But the existence of lungs and scuba tanks doesn't make the atmosphere excludable. (A commons is any good that is rival but non-excludable, as explained at http://libertarianmajority.net/public-and-private-goods.)
KB) "Monopoly"--what do you mean by that? (KBI mean monopolizing a non-material spatial resource -- a portion of the Earth's surface, or an orbit, or a segment of electromagnetic spectrum. The kind of monopolization I'm talking about applies only to space-time, not mass-energy. In the context of land this sort of site monopolization is called "enclosure".
KB) The first to build improvements (in the estate of nature) rightly acquire property title to those improvements. (KBYes: "Each person has full rights to his body, labor, peaceful production, and voluntary exchanges".
KB) there is nothing wrong with buying nearby property and slant drilling (KBIt's aggression to the extent that it diminishes the ability of the commons (here, an underground oil supply) to sustainably support its reasonable use by those with access rights to it.
KB) Pollution is wrong, not because it violates a "commons", but because it commits aggression against others. (KB"Violates a commons" is not a phrase I've ever used. What I've said is that it's aggression to impair one's equal right of access to a commons.