What is democracy? Or, more precisely, what do we want democracy to be? Because, of course, democracy is a social construction; it doesn't have any reality independent of what we think about how we want to organize our society.
Linguistically, "democracy" joins "demos" with "-cracy": rule or sovereignty of the people. Sovereignty is pretty straightforward (final legitimate decision-making), but what of "demos"? What do we mean by "the people"? There is no such thing in itself as "the people"; there are only individual people who happen to be acting more-or-less cooperatively. We can use "the people" metaphorically or idiomatically, but analytically, we have to talk about things we can actually look at, e.g. people and institutions.
We could choose to define democracy as strict majoritarianism, the absolute sovereignty of the majority. In other words, when we have any social question, we take a vote, and whatever the majority decides is the final decision in the matter. Note that particular institutional arrangements might or might not just indirectly effect sovereignty of the majority. For example, delegated democracy closely tracks sovereignty of the majority of individuals; a democratic republic, however, can substantially alter or block sovereignty of the majority (which is its whole purpose).
In the context of the United States in the 21st century, people tend to reject strict majoritarianism, for pretty good reasons. There are a lot of issues that can be decided by a majority without too many problems, but although we disagree about the specifics, almost everyone agrees that some things — e.g. private gun ownership or gay marriage — should be immune from the will of majority, at least in the short term.
If we take the rejection of strict majoritarianism as a given, the only alternative is to institutionalize the exceptions. In the United States, there are three sets of institutions that provide exceptions to strict majoritarianism. The first, as mentioned above, is republicanism (and the whole political infrastructure, including political parties, campaigns, campaign finance, etc.). The whole point of electing trustees is that, in theory, the trustees will wisely pick and choose between the will of the majority (specifically, how a majority of people would vote on any given issue) and the "good of the country." As I've discussed before, I categorically reject this institutional arrangement; our present trustees do not choose between the majority and the common good, but between the majority and the class interests of the bourgeois minority.
The class interests of the proletariat will more closely track the will of the majority, just because proletariat is in the majority. But even though socialism can be more majoritarian than capitalism, there are still important things that a lot of people would not want to be subject to the short-term will of the majority. We do not — or at least I myself do not want — for the majority to just vote on whether I live or die, whether I have freedom of movement, what I say, what job I do, whom I can or cannot have sex with, what kind of food I eat, etc.
The second institution that creates exceptions to strict majoritarianism is the legal system. Instead of just voting on whether I'm executed or put in jail, the "majority" (to the extent that republicanism is majoritarian) has to create a rule, which can be more-or-less objectively evaluated, and kill or imprison me only if I objectively violate the rule. And whether I have or have not objectively violated the rule is determined by an elaborate system of courts, trials, rules of evidence, precedent, lawyers, judges, juries, (and the associated political psychology) that distances the verdict from the majority.
At its most abstract level, a legal system seems like a Good Idea. Even if we don't at all restrict the kinds of rules majority can make, I really would prefer that the majority of people not just vote on putting me in jail, but control my behavior by making rules I can choose to comply with, and to which my compliance can be objectively determined. (Of course, the bourgeois legal system has a lot of institutional characteristics that are completely incompatible with socialism. Indeed, one good argument against capitalism is that capitalist employers, individually and as a class, can and do regulate behavior in ways that the somewhat more majoritarian government cannot regulate.)
The third institution, which is technically part of the legal system, but is important enough to be considered separately, is the institution of constitutionalism: the constitution categorically restricts the "majority" from making certain kinds of rules. Again, implemented judiciously, constitutionalism also seems like a Good Idea. But constitutionalism raises the question: if constitutionalism immunizes individuals from the majority, who decides what's in the constitution? If the majority creates the constitution, the constitution would not immunize the individual from the majority.
The critical point, however, is that constitutionalism immunizes the individual from the short-term will of the majority. Essentially, constitutional limitations on the majority comprise a list of things that a short-term majority has once done that a majority has later decided were Bad Ideas. For example, a majority might want to punish Alan for saying vile and hateful things about Norwegians, but Socrates might note that a majority of us have decided categorically not to punish people for just saying things. A majority might change that constitutional prohibition, but just the idea of changing the constitution at least forces the discussion to consider the abstract principle, rather than the immediate behavior. And, of course, we can also decide, as a majority, that we have more restrictions than just a majority vote — e.g. two-thirds majority — to change the constitution.
Thus, I believe that democratic communism can have its majoritarian cake and eats its exceptions too, with a socialist legal system and a socialist constitution.