A reasonably common type of question on RPG.SE is "Why does this rule exist" or "why is a rule this way?"
These questions come in several flavors, which are not mutually exclusive:
- "I hate this rule, someone justify it to me." Sometimes this is just a rant, sometime's it's like the "Sell me on..." questions you find on RPG forums.
- "I play other games and/or other editions of this game and that rule is different in those other games. Is it really different in this game? Surely it's a mistake."
- "I am houseruling or otherwise messing around with that rules set because I don't like its current form, but want to understand it more before changing it."
The majority of these questions had historically been closed as opinion-based.
Over the last couple years, answers about rules, especially with regards to D&D 5e, pushed past arguing pure rules as written and started to appeal to "RAI," or "rules as intended". Arguments arose about how "you can't know that" and how such answers are opinion-based, without actual statements from game designers as to the intent behind rules. But in the modern Internet world and especially with the D&D 5e designers, statements and tweets about the reasons behind game design decisions - their intent, how rigidly they are used by the designers, why they are a certain way - are more accessible than ever.
So we decided to try out a guided application of our universal SE norm Good Subjective, Bad Subjective to these questions, and require some kind of documentation about designer intent besides "well it makes sense to me" in these questions and answers. The tag designer-reasons was then applied to these questions as a marker to indicate the required quality bar.
This went kinda roughly. You can see some of the development of this on the many Meta posts on the topic about designer-reasons. Unfortunately, these questions still ended up pulling purely opinion-based answers.
Therefore a couple of weeks ago we asked how to save designer-reasons questions in How do we save designer reasoning questions?. The response was overwhelmingly, rather, to declare them off-topic.
The community found it was not able to effectively moderate these issues as a group and they are burning time and community goodwill disproportional to their value. People found questions that linger unanswered because no designer statements have been found irresistible to answer with opinions instead, and people would argue about their right to post their subjective opinions on these questions despite it being clearly outside our site's standard operating procedure.
So, are questions about the "why" of a rule on topic?