I would say that the best way to judge what is appropriate is to look at how much relevant data must be present for an answerer to address your problem.
If you're looking at a problem, like, say, "I have one user [A] who has been consistently harassing another user [B] in the community, and [B] has asked me to intervene and get [A] to stop. It seems that the [B] actually wronged [A], though. How can I best come to a resolution for this?", that has all of its relevant data being largely independent of the system and community that it is born in.
Contrast, for example, if you were on some small time forum and you have a user who you've IP banned but they just use a proxy to keep coming back in and your community tires of this user. The mechanical fact of your access to IP bans (and let's go with "nothing more elaborate than a simple entry of an IP and no other banning tools") is then the relevant data. That is a mechanical system, and you can parallel that with questions that relate to how the system here at Stack Exchange works with or against your needs as a moderator.
Mechanics aren't the only division. You could also consider policy. For example, we have a basic policy for suspensions which denotes an increasing length of 7, then 30, then 365 days for repeat infractions. It is flexible and allows for the moderator to use shorter (or perhaps longer) durations as necessary to adapt to an individual (such as one who has been a long-time positive user). If you're trying to assess a problem wherein such a policy is the major impact to the kind of decision you want to make, that makes the policy relevant.
So now that we've got this sphere of "relevancy" determines, let's then figure what matters of relevancy make it appropriate or not on this site. I would venture to suggest the two following guidelines at base:
If the question or its relevancy crosses a topic that touches less on "Advice and solutions from moderators" and more on "Guidelines and rules for acting as a moderator on Stack Exchange", then it should not be asked here. Or in other words, don't cross into the turf of material that should be asked on our support site of Meta Stack Exchange or the associated child metas, or things which should be covered in material such as the Moderator Help Center or the Teacher's Lounge. Those places should be the number 1 place for a moderator who wants to know what's up with this place in specific to go. This site should not be confused for a top-level resource for dealing with moderation as Stack Exchange. For more info, this question should probably cover it clear enough on this one.
Think about whether or not the relevancies for your question mar the ability to be useful outside of Stack Exchange. For example, if I ask some actually really good question about dealing with a problem user who has been downvoting another user across the site, while the question as a whole requires the relevancy of downvotes, the idea of "A user who is using the system malignantly to be mean to another user with means outside of direct textual contact" is something that might be useful to others. That starts to tread in the good line of things. But if I were to ask something like "What kind of approach should I take to handling flags for my site?", that relevancy starts to be waaay too narrow to be a good question. It's not to say that any question must absolutely be helpful outside of Stack Exchange, just that it's a good measure of what will probably generate a helpful and useful question as a whole.
