All communists are (lower-case) democratic socialists. We are of course socialists in the sense that socialism is a synonym for communism. More importantly, communism requires true democracy, in the literal sense of rule of the people.
Perhaps Solomon meant to describe himself as a (capitalized) Democratic Socialist. In its capitalized sense it has a more specific meaning: It refers to those who attempt to work for socialistic reforms within bourgeois "democracy". But bourgeois "democracy" deserves the scare quotes, because it isn't democracy in the literal sense of the word (and I don't mean the specious and irrelevant distinction between "republic" and "democracy"). All western "democracies" are bourgeois class dictatorships, where the people "rule" only in the sense that they are asked from time to time to choose between competing factions of the bourgeoisie.
It's important to understand that The United States was originally founded explicitly, intentionally and proudly as a dictatorship of the bourgeoisie: only white male property owners were originally granted the franchise. The central role of the bourgeoisie in our government is deeply embedded into all of our political and economic structures. The most obvious and compelling evidence is the critical role of money in elections, to the point where the key qualification for high political office is fund-raising ability.
One of the chief theoretical problems of communism is that there are few (if any) templates and historical precedents for literal democracy. Another problem is that ordinary people are deeply