I think most of us are familiar with the common semantic stopsigns like "God", "just because", and "it's a tradition." However, I've recently been noticing more interesting ones that I haven't really seen discussed on LW. (Or it's also likely that I missed those discussion.)
The first one is "humans are stupid." I notice this one very often, in particular in LW and other rationalist communities. The obvious problem here is that humans are not that stupid. Often what might seem like sheer stupidity was caused by a rather reasonable chain of actions and events. And even if a person or a group of people is being stupid, it's very interesting to chase down the cause. That's how you end up discovering biases from scratch or finding a great opportunity.
The second semantic stopsign is "should." Hat tip to Michael Vassar for bringing this one up. If you and I have a discussing about how I eat too much chocolate, and I say, "You are right, I should eat less chocolate," the conversation will basically end there. But 99 times out of a 100 nothing will actually come out of it. I try to taboo the word "should" from my vocabulary, so instead I will say something like, "You are right, I will not purchase any chocolate this month." This is a concrete actionable statement.
What other semantic stopsigns have you noticed in yourself and others?
While I agree with the reasonability of such a shorthand, what bothers me about this choice of term is that in mathematical usage, 'epsilon' generally stands for a variable, i.e. is bound by a quantifier: "for every epsilon > 0...", etc. Thus, although one informally thinks of such an "epsilon" as "a small number", the real point is that it's a number that "moves", usually "hitting" every positive number in some open interval containing 0. This is quite different from standing for a fixed but unknown number.
That seems like a not very persuasive complaint since even professional mathematicians will "epsilon" to mean a very small difference in an informal setting. To use a recent example from discussing a calculus midterm that we were going to make two versions, one of the professors said something like "the midterms will be within epsilon of each other" and no one batted an eye.