While not disagreeing with that ruling per se, both the question and the answer implicitly assume that the magic item in question isn't visibly unique. I would be very surprised to go into a kobold armory and discover that one random halberd on a rack of twenty is magical, or to find out that a totally mundane sharpened stick was actually a spear of lightning.![]()
I don't think I understand what distinctions you're drawing. Challenging a weakness might be "If you can't make the necessary stealth checks here, you'll have to fight the hobgoblin guards." Screwing the party would be "If you can't make the necessary arcana checks here, you can't have the reward for winning that fight." Or, more extreme, "If you can't make the stealth checks here, you can't complete the mission; you just lose."
Which player made the choice not to have a skill (like Arcana)? You keep saying "they", as if "they" were a person, making choices.They made choices that make some things harder in order to make some things easier.
Well, okay, if you say so, but the game as written today, 4th edition, not first, doesn't require that. It doesn't (at least by default) lump curses on you if you touch a magic weapon without checking it first. It doesn't suggest planting traps in every other hallway just to punish the party for being so foolish as to walk along without poking the floor with a stick. It doesn't suggest handing over lots of heavy but worthless treasure just to show the party how badly they screwed up for having nobody that can appraise effectively.But I rarely do "gimmes" with treasure. That's something earned, and discernment is part of the process. It has been since 1E. If nobody had appraisal, they'd better carry all the gems. If you don't have Identify, have a Dwarf to handle the stuff first or cash for the temple, etc.
But that's your choice. If you don't like "gimme" treasures, that's fine. My philosophy is to give out the treasure pretty freely; they've already earned it by getting past the combat, the puzzle, the trap, whatever the challenge was.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.