Earlier quoted context omitted.
Let's take an example, since they seem to work best: vaccines. Vaccines protect you from the risk of contracting particular diseases, some of which are crippling, lethal, or incurable. Plus, most are extremely effective: once you take your shots, you are effectively immune. That's good. There is a downside however. Sometimes, vaccines have side effects. Most side effects are quite benign, but if you're unlucky enough…
Are you actually arguing against giving anecdotes weight by using... anecdotes?
Here is the "good" version: Bayesianism is correct. Those who don't believe me may want to read E. T. Jaynes[1] or Eliezer Yudkowsky[2] (long, and may feel abstract and dull). But countless studies about biases showed that we humans are poor at correctly assessing evidence at our disposal. Some of those studies showed that some failure modes come from anecdotes. Downvoting seems harsh, but it's the best we currently have to combat those failure modes.
Now we don't want to overdo it. I suggest we put a comment citing which reliable statistics contradict the downvoted anecdote. Maybe that'll help avoid groupthink. We may also want to allow people to just say they have anecdotal evidence to the contrary of whatever.