People here use "distill" to mean "convert a dense technical document into a more easily readable form" despite it looking like it should have the opposite meaning.
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.
As a lawyer, I think that would be less the case because our jargon does not reflect reality per se but the consequences of the actions we make and the constructs we created as a society. But maybe I actually fail to see my friends and I doing it because people I mostly see are working in law.
In particular I'm thinking of computer programming jargon used in unrelated contexts ("My algorithm for choosing a restaurant to eat at...") just because all parties to the conversation happen to be computer programmers. I wonder, if there were a group discussing the same topics as on LessWrong, but composed predominantly of lawyers (or economists, doctors, etc.), would they also reflexively import their profession's jargon? How can we communicate in a way that doesn't unnecessarily confuse people of a different profession?
(To be sure, there's some stuff talked about here that is actually about computers, but there's also a lot that isn't.)
See also Style Guide: Not Sounding Like An Evil Robot. ("Humans" instead of "people" is the one I notice most.)