The “common wisdom” being investigated in this study and discussed in this thread was whether short and “shocking” cold showers would improve health. The top-level commenter claims that transitioning directly from a hot shower to a few minutes of cold shower at the end has made him less susceptible to respiratory viral infections.

I agree that there are often several directly contradictory pieces of “common wisdom” floating around about health topics. That’s one of the chief difficulties with folk advice in general.