I don't understand enough about the economics to understand what kind of philosophy a deflationary currency entails. Can you please explain?
As to the decentralised nature, I'm not convinced that really appeals to any deep philosophy other than our greedy nature to want to be able to own what we think we should own.
Essentially, a deflationary and decentralized currency encourages "our greedy nature" rather than discouraging it. Inflation is often referred to as a subtle tax, because it devalues currency. Thus, you're incentivized to spend your money rather than save it. Deflation, as the inverse, increases value of currency and incentivizes you to save your money rather than spend it.
There's nothing particularly deep about libertarian philosophy. (Though there are different amount of nuance depending on which flavor of libertarian you manage to get into a conversation with. Some of them are competent thinkers; I have found them to be exceedingly rare.)
Many flavors extol the virtues of selfishness, though. You'll find this is particularly true with libertarians who agree with Ayn Rand. Even those who don't will generally say that people should look to their self-interest (it no longer appears popular to invoke the invisible hand at this point; maybe because of the intervening years of people noticing that Adam Smith had a lot to say that contradicts libertarian ideas) and use abstract forces like the price mechanism to determine policy. (This is a very rough sketch.)
...and anyways, I'm spending too much time trying to be fair. Libertarianism is fucking stupid, which is an opinion I have based more on its political bits, which is a teenager's idea of society, than on its economic bits, which I'm willing to concede more because I'd rather claim ignorance than because I think there's any merit there.
The point is that looking out for number one is a cornerstone of varying intensity in libertarianism and Bitcoin's deflationary and decentralized nature plays very directly into that.
As to the decentralised nature, I'm not convinced that really appeals to any deep philosophy other than our greedy nature to want to be able to own what we think we should own.