I also saw that triangle shaped plot and had the same thought. I read a great paper about this recently [0] with some of the same examples as the link in the parent, but going a little further in depth.
I originally got on this topic when reading Bayesian Methods for Hackers [1]. I am still hunting for a good method to correct/compensate for this when I am doing these types of comparisons in my own work.
When I was writing my thesis I wanted to correct for that as well, and weighted my data by the log of the sample size. This made intuitive sense to me, and both my advisors seemed to agree, though neither of us found compelling papers for this.