Here is what I was referring too: "If you want to have organically grown food as a lifestyle choice, you have to become a farmer. Or get it from a farmer, perhaps by trading some other skill."
Trading some other skill for organic foods is barter.
I'm aware of that, but since the system I was describing explicitly states that such a trade is optional to the system, the system I'm describing isn't barter. I even mentioned an example where it was not (Sisko's family restaurant).
Now to the other part of the question: All societies that exist or have existed have elements of capitalism, socialism, and communism in them. While we consider the system in use in the USA to be capitalism, we have elements of socialism and communism. Even the Soviet Union had capitalistic elements. Just not that many. When I call a society a capitalistic, socialistic or communistic society, I'm referring to the overall. Is it mostly socialism? Is it mostly capitalism? There are plenty of examples I could pull from any (real) society you can name for all three systems. Communism being the hardest to find of course given our society's disdain for it, but it is still present.
Now as for Star Trek, you first must keep in mind that it isn't real. Depending on the author who wrote the book/movie/short story/etc., you will find varying degrees of each system. And I'm talking about just within the Federation. I'm not talking about Klingons, Romulans, or Feregi. Even the movies can't agree. In some shows, walk into a bar and order a drink. No reference to paying. Customer walks out. Walk into another bar and you pay or you leave. And in still another you're told your credit's good. Even in Quarks bar, I never saw Mr. O'Brien pull out a slip of gold pressed latinum to pay for his Ale and he certainly ordered quite a few throughout the seven years DS-9 ran. Now Quark did make many references to putting it on his bill which confirms there's a system of money but then why the speech between Lilly and Picard in First Contact about not being paid? Picard's answer was, "we work to better ourselves." OK. So how did Mr. O'Brien get credit to pay for his bar tab? And while a society could be a communistic society, that wouldn't stop it from trading with others. It makes goods and services and while it might not use money internally, it can externally.
1. Support for the assertion that the system is "likely communistic" cannot come from the observation that the system is fictional and ambiguous. That's what I call a self-annihilating argument.
2. To assert something is communistic its not enough to claim it shares aspects of communism; it must share unique aspects of communism that distinguish it from competing systems. Both communism and socialism (in its various forms) incorporate the notion of social ownership or control of the productive output of the economy, but where they diverge is that communism purports as its goal a form of unlimited democratic control of governance and economic control while socialism is more flexible in incorporating markets and hierarchical control. A major distinction is that a common paraphrase of communism is "from each according to his ability, and to each according to his
need"; the respective socialism version is "from each according to his ability, and to each according to is
contribution." Beyond the essentials, socialism contains an element of meritocratic reward that communism does not, and its evident in Star Trek that people who contribute exceptionally can benefit exceptionally, just not generally to the impairment of others.
More specifically, communism espouses the notion of an abolishment of private property. Socialism distinguishes private property from the social commons, or public property, and both coexist.
There has never been an example of a pure communistic system, but that's irrelevant to the question of which system Star Trek is depicted to have most resembles. In every respect it resembles communism, its a property of communism that overlaps with socialism. Beyond that, it contains socialistic elements that are inconsistent with communism. If you can name an aspect of the economy that is depicted in Star Trek that is associated with communism and *not* associated with socialism, I would be prepared to reconsider. And I'll toss out the first one that fails the test: although characters have stated at various times that "money doesn't exist" or "money isn't used" in the time of Star Trek, that's an apparent colloquialism because those statements do not override cases where money is actually used or explicitly stated to exist, just in narrow cases. They also use other colloquialisms that state the opposite, such as "you've earned your pay for the week." Those clearly aren't statements of economic fact.