I've noticed people using formal logic/mathematical notation unnecessarily to make their arguments seem more "formal": ∀x∈X(∃y∈Y|Q(x,y)), f:S→T, etc. Eliezer Yudkowsky even does this at some points in the original sequences. These symbols were pretty intimidating to me before I learned what they mean, and I imagine they would be confusing/intimidating to anyone without a mathematical background.
Though I'm a bit conflicted on this one because if the formal logic notation of a statement is shown alongside the English description, it could actually help people learn logic notation who wouldn't have otherwise. But it shouldn't be used as a replacement for the English description, especially for simple statements that can easily be expressed in natural language. It often feels like people are trying to signal intellectualism at the expense of accessibility.