"Federated" like email is. There are different "instances," you are on Lemmy.world, I am on Lemmy.ml. We can talk to each other because Lemmy.world and Lemmy.ml are federated, ie linked, just like Lemmy.world is linked with many other instances. Unlike Lemmy.ml though, Lemmy.world is defederated from instances like Hexbear.net and Lemmygrad.ml, so while I can see them and interact, you cannot. That's a good thing for some people, and bad for others, the "free speech absolutists" tend to like Lemm.ee or other general purpose instances federated with as many instances as possible.

Each instance has its own rules, communities, and flavors, so each can provide something unique. Lemmy.world is a generalist instance, like Lemmy.ml.

As for nostialgia for the Socialist system, it's well-documented. Polling is consistently favorable towards the Socialist system, even if we check different polls. There are a number of reasons for this, from simple nostalgia to the old days to simple fondness for youth, but the most consistent answer is economically.

Contrary to your suggestions of mass starvation, outside of the struggles with collectivization in the 1930s and World War II, where the Nazis took Ukraine (the USSR's breadbasket) at the start of the war, food was secure. The CIA even documented this internally, favorably comparing the nutrition to US nutrition. This is also supported by a doubling of life expectancy from the Tsarist system, gradually increasing over time.

The biggest reason why Soviet nostalgia exists, is because life was easier for the working class. There was comprehensive and free healthcare, education, and childcare, housing was affordable, economic growth was consistently rapid and positive while wealth inequality was low, and there was a general degree of hope throughout. Scientific achivement was celebrated, including the first man and first woman in space, despite being feudal half a century before. Stephen Gowens has a good article titled Do Publicly Owned, Planned Economies Work? that goes over the myriad strengths of the Soviet Economy, as well as where it faltered, and partially why the USSR was eventually dissolved.

With the dissolution of the Socialist system came a collapse of the economy. Prostitution, drug abuse, crime, and poverty all skyrocketed. New luxuries were available for those who could afford them, but an estimated 7 million people died from the lack of food security throughout the world due to the economic collapse.

The reasons behind its dissolution included the following problems:

1. Liberal reforms that gave the Bourgeoisie power over key industries (such reforms were actually a major desire of the 1968 Dubcek platform, in even greater quantity, hence why it was shut down by neighboring Warsaw Pact countries)

2. A firm dedication to planning by hand even as the economy grew more complex and computers too slow to be adapted to the planning mechanisms

3. A huge portion of resources were spent on maintaining millitary parity with the US in order to dissuade US invasion

4. 80% of the combat done in World War II was on the Eastern Front, and 20 million Soviets lost their lives, with no real economic support from the West in rebuilding despite taking the largest cost of war

5. An enclosed, heavily sanctioned economy relied on internal resource gathering, closed off from the world market

Countries like the PRC have taken to heart what happened in the USSR. As an example, the PRC shifted to a more classically Marxist economy, focusing on public ownership of only the large firms and key industries, and relying on markets to develop out of private ownership. This keeps them in touch with the global economy without giving the bourgeoisie control of key industries, and thus the bourgeoisie has no power over the economy or the state.

The PRC is where the USSR is really succeeded. It's an astounding achievement, and proof that Socialism not only works, but excels, and is indisputably the way foward, all the way into Communism. There are also other Actually Existing Socialist states that carry the torch, such as Cuba, the DPRK, Vietnam, Laos, and to a smaller extend Kerala, the Sahel States, Venezuela, Belarus, and more.