The belief that using more complex and longer words will make a text seem better written (and the author deemed more intelligent) is highly prevalent among students at all levels of the educational system. However, previous literature has proven this to be a myth: writing simpler and clearer leads to better outcomes. Processing fluency –the subjective experience of ease with which people process information– reliably influences people’s judgments across a broad range of social dimensions. Nevertheless, prior studies on this phenomenon have primarily focused on how people process written texts at the individual level. In this work, we ask whether linguistic complexity reduces the perceived validity of arguments on controversial moral issues, and whether it also affects the likelihood of people reaching consensus on those issues. We focused on the effect of word length (a previously established standard index of linguistic complexity). Three studies, comprising a large-scale behavioral study (N=10,548), a group deliberation study conducted in online chatrooms (N=768), and a pre-registered randomized controlled experiment where we manipulated word length (N=600), consistently showed that the use of longer words leads to weaker argumentation. In short, these results suggest that brevity and simplicity are key drivers of effective argumentation and deliberation on controversial moral issues.