Could the quality of a substantial fraction of argumentation in the “reality-based” community be explained by countersignaling? In the standard example of countersignaling, rich people who are known to be rich will regard spending money conspicuously as vulgar since only parvenus need to signal their wealth.
Similarly, if reality-based bloggers figure that everybody knows them to be rational, they might not bother with such minor things as evidence since only irrationalists need to signal rationality. It's not signaling, it's countersignaling. (I was inspired by the level of discourse in the comments here.)
This is an alternative to the theory that they have rationality offsets.