I think this is the kind of question that needs to be prefixed with "why do you want to know?"
I mean, they're technically historical in the same vein as "who invented experience points." And they're objective, and so on. But they can also be pretty much just transcribing from a set of rulebooks (general reference), and extremely narrow in general interest.
If someone is looking to move from one edition to another, then they should scope the question to those two editions. Nothing is gained by obfuscating the actual intent of the question, and scoping the question properly improves the odds of generating a solid answer (because answerers need to know a smaller set of editions).
So far as knowledge for the sake of knowledge, compare this question on the Darkness spell to this question on turning undead.
The question on darkness demonstrates research on the part of the questioner, looks at specific aspects of the spell, and probes for reasons behind the design of the darkness spell.
The question on turning undead just asks for a multi-edition rules dump.
So, I would say that "yes, questions about how the rules have changed can be on topic, but no, that question on turning undead is not (or at most is an extremely marginal question)."