I feel comfortable saying you can own a .onion address, since it's controlled by a private key you control.
Properties are dependant on you being able to defend it, which, if you aren't a state, you delegate to the state where you posess thing. This include your body, your mind, and your life.
Just because you can redefine a word into being meaningless doesn't mean it's useful to do so.
Losing a couple percent of cash every year to inflation is a lot more predictable than losing a domain suddenly and having someone else put up a malware-infested copy of my own site taken from an archive.
This is true but it would nice to have some TLDs operated as associations or coops for the benefit of members.