That's not really a rationality issue. That's people implicitly saying "I don't know anything about this subject or find it boring. Here's something else I'd rather talk about."
I read that response as saying: gold price is affected by how much gold is out there. If we thought gold was only produced by extremely rare events like neutron star collisions, we couldn't explain the amount of gold apparently present on Earth; and we would conclude there's less gold than we thought (perhaps people are passing something else as gold). The price of "true" gold should go up if this new physical theory is confirmed. If it's going down, people disbelieve the theory.
Alternatively you could read that as saying: the price of gold isn't...
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?