In the Kalaripayattu question Matt Chan asked 'effective for what?', Dave Liepmann made a very good comment in response that by default we should assume that it means effective at fighting. I think it would be good if this becomes an official policy, to have a site-wide assumption that martial arts are about fighting, and that people are asking questions about being better at fighting.
Rather than trying to establish some local standard (that outsiders won't necessarily be aware of, and may struggle to learn as they acclimate to the site), why not just... Edit unclear questions?
Now, being a naive outsider, I would tend to assume that questions on a site named "Martial Arts" would be about fighting. So if there's any ambiguity in a post, editing it to clarify with that presumption would be appropriate - and if it turns out you're wrong, prompt the author to clarify himself.
Either way, the end result is an increase in clarity.
In most situations, I would expect there to be relatively little ambiguity to begin with, so no action (or implicit, site-local humpty dumptyism) is needed.
I don't think it is a good idea to "have a site-wide assumption that martial arts are about fighting." That is certainly one application of martial arts, but there are plenty of martial arts that aren't about "fighting" or, at the least, are either fairly far removed from their roots or have significant priorities in addition to anything regarding fighting.
Certainly, even beyond that, there are reasons people practice martial arts beyond "being better at fighting."
Robin, I see your point, but have to disagree.
Aikido belongs on MA.SE. Aikido is almost always not about fighting. (That doesn't preclude mentioning how terrible it is at producing fighting-capable individuals.) So right away, I have to disagree with your proposal. (Shog9's answer, as usual, also has the correct.)
The problem here is not a standard about fighting being the default. It's that a number of fairly obvious topics are strangely off-topic or viewed with disdain by the general MA.SE user base. For instance: comparing styles (which you and I agree should be on-topic), or that fighting is by default always relevant in martial arts.
When someone asks for a "plain comparison" in the context of a recommendation, I think it's pretty plain that we should both keep the question and take it as a question incorporating effectiveness at fighting as well as ancillary goals (which would, ideally, be explained in detail). My concern is that the question was close to closure because mods saw it as a style-comparison/effectiveness-at-fighting question, which is patently absurd in my view. (Such questions have a lot of value pretty much as soon as they get more specific than "which is better herp derp".)
I think that me and you and other users having the assumption that martial arts are about fighting is enough. I even believe that martial arts have other purposes--health, community, a sense of meaning--but that doesn't take away from the fighting being central.
The original poster on the example question even noted that he or she was only asking for a plain comparision in response to my question about what efficacy the asker was seeking.
The problem with creating this assumption is that it is narrowing the idea of what martial arts as a whole encompasses. Like what David H. Clements stated in his answer, martial arts doesn't have to be entirely about fighting.
What makes the assumption narrowing that prescribing an assumed meaning for the question removes the onus of the user to effectively communicate what to ask, to be clear and descriptive of the . One reason is to maintain quality on this site, but another is to hope that users will learn to improve in this regard. Users shirking responsibility to put effort into a question is a reflection of the the irresponsibility of the site and those that contributing and participating in this site.
Keep in mind that not everyone here also is a native English speaker. It would be a disservice to those who aren't able to word their thoughts are well as others who are fluent in English (and sometimes I question native speakers too) by creating a site-wide assumption for a set of few words.
In short, this is a bad idea and ultimately doesn't benefit the site.
I've been thinking about this question, going back and forth in my mind and struggling to answer. Then I found the following on Eric Raymond's blog. Different schools and styles answer to different purposes. When speaking of these, martial artists commonly describe three categories: combative (practical self-defense), sport (competitive fighting), and do (self-control and self-improvement; this may just mean physical fitness, but in some arts shades into meditation and mysticism, most often of a Buddhist or Taoist variety).
I think he's said that rather well; "effective" doesn't always mean combat; different people do martial arts for different reasons, and "effective" means that martial art advances your particular goals.
updated partly based on R. Ashe's excellent comments I feel the need to add some caveats. 1) I strongly support the notion that MASE is about answers, not discussion. That said, I think that some empirical responses can be legitimate answers even without ordinal measurements. 2) I'm nervous about "combat effectiveness" as the gold standard. Every art makes assumptions about the types of attacks and attackers. Every art compromises "effective" in favor of "safe". (different arts make different compromises). We have had some students come to our dojo and leave because we practice a more "pragmatic" style, and we've had some students leave because we were insufficiently "street lethal". I'm very reluctant to conclude that either of those groups of students weren't practicing or looking for "legitimate" martial arts. I believe it was one of the Northern Wind instructors who pointed out that very few "real" fights occur on tatami mats, but I think most of us practice in such an environment. I don't disagree that "effective = combat" is a useful yardstick, but
Ultimately, I think this is a useful standard, but not one we should try to enforce.
From the FAQ:
Theatrical or stage combat that focus more on theater or entertainment (for role-playing, re-enactments, etc.) (off-topic)
Fitness issues unrelated to martial arts (off-topic, please ask on Fitness & Nutrition)
So we've got 2 topics that are already outlawed here. First of all, how do you define that a fitness issue is unrelated to martial arts, and blocking discussion of theatre and entertainment already precludes discussing another non-combative application of martial arts.