Is people believing in Christianity significantly more likely under the hypothesis that it is true, as opposed to under the hypothesis that it is false?
Yes.
Once one person believes in Christianity, does more people believing in Christianity have significant further marginal evidentiary value?
Yes.
Does other people believing in Christianity indicate that they have knowledge that you don't have?
Yes.
(Weakly.)
I agree completely. It's impossible for me to imagine a scenario where a marginal believer is negative evidence in the belief - at best you can explain away the belief ("they're just conforming" lets you approach 0 slope once it's a majority religion w/ death penalty for apostates).
r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.