If 80% of posters on a thread about diets say vegetarian is healthier, and 80% of posters on a thread about fun recommend riding a motorcycle, it doesn't follow

If 80% of posters on a thread about diets say vegetarian is healthier, and 80% of posters on a thread about fun recommend riding a motorcycle, it doesn't follow that there is a single HN zeitgeist saying both things. A simpler explanation is that there are two groups which speak up in different situations. Those groups don't necessarily overlap much.