Sometimes, someone asks a question that seems like it might suffer from the XY Problem (asking about your attempted solution instead of your actual problem) and you want to point that out. Or you feel that something about the question frame makes answering the question invalid and the only tenable answer is mu. Or, you just strongly disagree with something they're doing as revealed in the question and wish to challenge its frame. How do we do that in a constructive manner within the RPG.SE format?
If it is really a case of asking about the solution instead of the problem, it's OK to leave comments of the form "Can you state the real problem you're trying to solve so we can suggest alternate solutions?" or similar requests for more information (if it's relevant/needed).
However, in some cases there is already a solution domain chosen and that's OK. Comments like "you shouldn't do that" are not welcome or on topic. There are a lot of different gaming styles out there and different game systems, and critique of those in comments is not a legitimate use of comments on this site. See Why are site comments being deleted? for more on comment use here. Comments like "you shouldn't try to do X in your game" or "you shouldn't use system X for that" will be deleted per that policy.
You need to be careful when challenging the frame of a question - the line between that and threadcrapping can be a narrow one. You should:
- Provide your critique as part of an otherwise legitimate answer. This isn't strictly required, but we very strongly recommend it. Sometimes declining to answer the question and instead going straight to a frame challenge — e.g. “don't do that at all” — is the right answer, but it's also risky and liable to backfire. This is a judgement call for the author and voters to handle. In most cases you should spend more time answering the question than in challenging it.
- Do it carefully and support your challenge - "I prefer different things" is not really a good reason, remember this isn't a forum and the goal of the site is to solve people's problems, not to wave our own personal freak flag around.
- Don't get upset if you get voted down because the community thinks you overstepped your bounds. You know you're taking a risk by doing it instead of just answering their question.
- Don’t just say you’re “challenging the frame” or “this is a frame challenge”. For every RPG Meta insider who knows what that means, you just confused a hundred regular users and a few thousand non-user readers from Google who don’t understand what you just said. Saying you’re frame challenging isn’t a replacement for actually challenging the frame. Don’t say it: do it.
I've tried to provide an example of an answer following this guidance in 5th level optimized Fighter/Ranger builds for 3.5/Pathfinder, where we had started to get comments questioning the asker's intent to introduce optimization to his game. I agreed with those sentiments, so made an answer that answers the question but brings up the "violence inherent in the system" as well.
Also remember sometimes you can see the XY problem everywhere because you can always recur up an additional level of generality. "Well your real problem is using system X in the first place," "Well your real problem is liking immersion/charop/whatever in the first place..." These aren't really the XY problem. If you want to tell someone e.g. they "can't roleplay in D&D" and should pick a different game system - well, you're wrong, but otherwise, you should make some suggestions to that end ("I've had more success with evoking the mood you're looking for in other games") as a rider on an answer about how to actually accomplish their stated goal.
Also note that if the question asker specifically addresses your concern proactively, you are pretty much off topic. People legitimately disagree, and you are not helping the person if you are going down a path they have explicitly stated as off topic. For example, in my question on How do you help players not focus on the rules?, I proactively noted that I understood not everyone wants that playstyle but that is not relevant and I want answers from that frame. Of course, if a questioner asks a question and rules out what everyone considers to be the sensible paths - then they get no good answers, and they reap what they sow.