And sure enough, someone has done this in another front page post:

https://news.ycombinator.com/item?id=5391677

(edit: which is why, even if the parent is somewhat tongue in cheek, I'm complaining about it, heh.)

The problem is that fallacies are not always fallacious. In fact, I'd guess that the majority of online arguments which people label with names of fallacies are not completely invalid, though they may be less valid than other arguments.

The fallacy in calling something a fallacy, so to speak, is that while an argument that includes a fallacy cannot rigorously prove that something is true, your typical discussion where fallacies are brought up is not an attempt to rigorously prove something, and cannot be, because it's about an inherently subjective statement or one which not enough information is available to prove or disprove. To advance the discussion in that case, an argument need only demonstrate that the statement is somewhat likely to be true - from a Bayesian perspective, that a rational actor should assign a higher probability to the statement being true than if he did not consider the argument - and many "fallacious" arguments satisfy this criterion.

For example, a slippery slope argument is best substantiated by justifying why doing X is actually likely to lead to doing Y, but even without substantiation, pointing out that Y is a possible outcome logically makes X a slightly worse idea to consider, and there is a lot of room in between for partially but not fully substantiable arguments. Or to pick a random example from the site, an appeal to nature is fallacious because "because something is 'natural' it is therefore valid" is not necessarily true, but while it's easy to put excessive credence in the correlation between "natural" and "good", that doesn't mean there is no correlation: in the absence of stronger evidence to the contrary, "it's good because it's natural" is a valid starting point. Even the mainstay of fallacies, ad hominem, is subject to this: because arguing about subjective points necessarily involves taking a bunch of factors and assigning them essentially arbitrary weights (theoretically based on one's experience of what factors have proved accurate in the past, but still arbitrary), it's perfectly valid to argue that because someone has demonstrated bad judgement in the past (especially about a similar judgement call, as in the post I cited), their assignment of weights in this case is more likely to be incorrect.

A response of "this is fallacy X" is itself quite valid as a heuristic argument - an argument containing a fallacy is less likely to be valid than an argument not containing a fallacy - but it's not sufficient to completely dismiss most arguments, and those who would use the rhetoric of logical fallacies to purport to do so, linking to a well-designed web page that says "your argument is invalid", are essentially committing the fallacy of arguing from authority. While certainly not all arguments deserve well-reasoned responses, just claiming that an argument is a fallacy is generally not a well-reasoned response, and in practice it tends to be rude and unproductive. Linking to a description of a logical fallacy carries a certain implication of "your argument is so bad that you need to be educated about the basics of fallacies". It's like saying RTFM - reasonable in response to a poorly formed or low-effort question, but rude in response to a high-quality one.