Ones I've noticed are "lazy" or "stupid" or other words that are used to describe people. Sure, it can be good to have such models so that one can predict the behavior of a person, like "This person isn't likely to do his work." or "She might have trouble understanding that." The thing is, these are often treated as fundamental properties of an ontologically fundamental thing, which the human mind is not.
Why is this person lazy? Do they fall victim to hyperbolic discounting? Is there an ugh field related to their work? Do they not know what to do? Maybe they simply don't have good reason to work? Why is this person "stupid?" Do they lack the prerequisite knowledge to understand what you're saying? Are they interested in learning it? Do they have any experience with it?
The thing is, these are often treated as fundamental properties
Being stupid is a fundamental property ("stupid" understood as having low g and not an inability to understand some particular issue).
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?