My understanding is that the karma toll is charged only when responding to downvoted posts within a thread, not when responding to the OP.

You could be correct there.

I didn't say that the only correct definition is the most popular one; you are shading my position to make it more vulnerable to attack. My position is merely that if, as you yourself said, "everybody" uses a different definition, then that is the definition. You said "everybody is silently ignoring what the fallacy actually refers to". But what a term "refers to" is, by definition, what people mean when they say it. The literal meaning (and I don't take kindly to people engaging in wild hyperbole and then accusing me of being hyperliteral when I take them at their word, in case you're thinking of trying that gambit) of your post is that in the entire world, you are the only person who knows the "true meaning" of the phrase. That's absurd. At the very least, your use is nonstandard, and you should acknowledge that.

There's a conditional in the sentence that specifies "everybody". "So if I'm arguing against a straw man..."

I don't think I -am- arguing against a straw man. As I wrote directly above that, I think your understanding is drawn entirely from the examples you've seen, rather than the definition, as written on various sites - you could try Wikipedia, if you like, but it's what I checked to verify that the definition I used was correct when you suggested it wasn't. I will note that the "Sunk Cost Dilemma" is not my own invention, and was noted as a potential issue with the fallacy as it pertains to game theory long before I wrote this post - and, indeed, shows up in the aforementioned Wikipedia. I can't actually hunt down the referenced paper, granted, so whether or not the author did a good job elaborating the problem is a matter I'm uninformed about.

Presumably, your line of thought is that what you just presented is absurd, and therefore it must be wrong. I have two issues with that. The first is that you didn't actually present what your thinking was. That shows a lack of rigorous thought, as you failed to make explicit what your argument is. This leaves me with both articulating your argument and mine, which is rather rude. The second problem is that your syllogism "This is absurd, therefore it is false" is severely flawed. It's called the Sunk Cost Fallacy. The fact that it is illogical doesn't disqualify it from being a fallacy; being illogical is what makes it a fallacy.

"Illogical" and "Absurd" are distinct, which is what permits common fallacies in the first place.

I sincerely believe that you are using the phrase "sunk cost fallacy" that is contrary to the standard usage, and that your usage impedes communication. I attempted to inform you of my concerns, and you responded by accusing me of simply trying "score points". I do not think that I have been particularly rude, and absent prioritizing your feelings over clear communication, I don't see how I could avoid you accusing me of playing "games of trivial social dominance".

Are you attempting to dissect what went wrong with this post?

Well, initially, the fact that everybody fought the hypothetical. That was not unexpected. Indeed, if I include a hypothetical, odds are it anticipates being fought.

It was still positive karma at that point, albeit modest.

The negative karma came about because I built the post in such a way as to utilize the tendency on Less Wrong to fight hypotheticals, and then I called them out on it in a very rude and condescending way, and also because at least one individual came to the conclusion that I was actively attempting to make people less rational. Shrug It's not something I'm terribly concerned with, on account that, in spite of the way it went, I'm willing to bet those who participated learned more from this post than they otherwise would have.

Perceiving an assertion of error as being a dominance display is indeed something that the primate brain engages in. Such discussions cannot help but activate our social brains, but I don't think that means that we should avoid ever expressing disagreement.

I'll merely note that your behavior changed. You shifted from a hit-and-run style of implication to over-specific elaboration and in-depth responses. This post appears designed to prove to yourself that your disagreement has a rational basis. Does it?

My immediate motive is to impart knowledge. I suppose if one follows the causal chain down, it's quite possible that humans' desire to impart knowledge stems from our evolution as social beings, but that strikes me as overly reductionist.

Case in point.

Let's suppose that is your motive. What knowledge have you imparted? Given that you're concerned that I don't know what it is, where's the correct definition of the Sunk Cost Fallacy, and how does my usage deviate from it? I'd expect to find that somewhere in here in your quest to impart knowledge on me.

Your stated motive doesn't align with your behavior. It still doesn't; you've dressed the same behavior up in nicer clothes, but you're still just scoring points in an argument.

So - and this time I want you to answer to -yourself-, not to me, because I don't matter in this respect - what exactly do you actually want out of this conversation?