I cannot address this question without lifting a quote from The Joys Of Yiddish
The first riddle I ever heard, one familiar to almost every Jewish child, was propounded to me by my father:
"What is it that hangs on the wall, is green, wet -- and whistles?"
I knit my brow and thought and thought, and in final perplexity gave up.
"A herring," said my father.
"A herring," I echoed. "A herring doesn't hang on the wall!"
"So hang it there."
"But a herring isn't green!" I protested.
"Paint it."
"But a herring isn't wet."
"If it's just painted it's still wet."
"But -- " I sputtered, summoning all my outrage, "-- a herring doesn't whistle!!"
"Right, " smiled my father. "I just put that in to make it hard."
By which I mean to say: "no".
I think there are allowable ways to mislead the reader. Taking the puzzle you link to merely as an example, I would say that putting the markings on a ring belonging to Gollum, and having them glow like the script on the One Ring in LOTR are absolutely fair play. The markings look to me more like Dwarven runes so I would also call it fair to say he pulled it from the finger of a dead Dwarf lord. I would even call it fair (but beyond what I personally would do) to add a sentence saying: "For those interested in the various scripts of Middle Earth see..." and provide links. Better would be to modify the last line of the problem statement to be:
he can't wait to go back home to use an elvish dictionary.
I would call that fair but inartistic. Ideally, you want to lead the reader gently astray and this feels more like pushing him off the path.
A misleading hint comes in a different class. I believe that when you write "Hint:" and put in a spoiler tag you are giving meta information about the puzzle. It is part of the puzzle statement or the conditions for solving it. You can make your hints tricky, I myself have been accused of being "sly", or you can give hints that only make sense after the puzzle has been solved. It is not fair to directly say that something has bearing on the solution when it doesn't. I believe it is the same principle as adding misleading tags.
I think the appropriate response is a downvote and a comment explaining why. That's my take on it.
