Good shitposts come out of provocation, and there's always a little bit of insight communicated in effective provocation. Unless you're dril, it's hard for a poster to access that insight without betraying some trace of sincerity. The normal failure-states for shitposters are an excess of sincerity (EG gimmick accounts dropping the bit to repeat a slogan) or self-betrayal, which amounts to a loss of insight.