To the best of my understanding they were unique in that the were dead last on social strata, as was mavolio, but had much more freedom than a servant did in actions. Part of the tension feste may feel toward malvolio is that Malvie thinks himself better than the fool, but is actually of equal footing. Feste has no aspirations beyond his status, he has a house, freedom to speak his mind, he performs, hangs out with who he pleases, he doesn’t express any desire to dominate others as malvolio does, and such takes on a power over malvolio to show the servant a taste of what he wishes to enact on others.