[hythloday]

I generally disagree with the OP and agree with your dissent, but do you not think that the OP could be more charitable read, not as "suppress certain kinds of replies", but as "don't exploit known cognitive biases, and punish people who seek to exploit them"? I'm quite comfortable downvoting naked appeals to emotion ("please won't someone think of the children?"), because I don't think they add anything, and are harmful to, the conversation. I think the OP is making a similar proposal for anecdotal contradiction. Both his examples are chosen well in this light: non-medical replies to a study that found a weak correlation. To me, the contradictions look more like a strawman: the argument they attack seems to be that coffee consumption will, in 100% of cases, cure Alzheimer's, a claim the study never made. I'm not sure we should privilege (or penalize) anecdotal contradiction on anything other than the merits of its argumentation, but in many cases I find that to be extremely weak.

[kijin]

But how do you distinguish between people who simply share their stories because they think it's moderately relevant to the thread, on the one hand, and people who "exploit known cognitive biases", on the other? Exploitation seems to imply deliberate manipulation, which most people who share medical anecdotes don't intend at all. Yet, humans have so many cognitive biases that even the most mundane thing can trigger one or another bias.

[hythloday]

"Trigger" is a better word than "exploit", in some ways, but it makes it sound like it's an accident: "sorry, I just fell over your cognitive bias, I had no idea it was there!". In fact I think people have a weak responsibility in good discourse to be aware of known cognitive biases and not to appeal to them. I'm comfortable downvoting people who appeal to emotion even if they're not setting out with the intent of doing it, simply because I think it leads to a worse discussion.

You distinguish between people who are sharing anecdotes and people who are making strawmen arguments in the usual way that you'd distinguish them - by tone, follow-ups, etc. But if your sole contribution to a thread is "me too" (or "actually, not me too"), maybe that contribution isn't particularly valuable in itself.

[mindcrime]

I'm comfortable downvoting people who appeal to emotion even if they're not setting out with the intent of doing it, simply because I think it leads to a worse discussion.

And I'm comfortable making a "corrective upvote" because I think downvotes should be reserved for obvious spam, completely OT comments and comments that add nothing to the discussion at hand.