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?
In academic context, especially physics: "It is obvious" and "handwaving"
The first silences any dissent by implicitly marking anyone doubting the intuition as stupid. The second marks the argument as imprecise and thus implicitly worthless though the "handwaved" argument might be a nice idea with the need to be enhanced.
We used to deliberately switch "it is trivially obvious to the most casual observer that ..." to "it is casually obvious to the most trivial observer" in order to remind ourselves that "obvious" doesn't always mean what it means.
I once saw a heated argument between two bell labs scientists where A was shouting at B "you are wrong, you are just wrong" and after 1/2 hour of loud discussion in A's office the door opened again at which point I heard A now shouting at B "your point is just trivially obvious." I thought that was pretty good, moving a PhD Princeton Astronomer from "wrong" to "trivially obvious" in less than one hour. Agile minds!