Chaosmancer
Legend
I don't think a 12th-level character can die to a 30-foot pit trap (exception: in roll-for-h.p. editions where the 12th-level character still only had 18 h.p. or fewer; but said character would never have made it to 12th level in any event).
The question of whether high-level characters could or should still be threatened by relatively minor things like this is a much bigger one, and brings in questions around power curve, long-tail bell curves, and so forth.
Of course they can. You don't encounter all traps at max hp.
All true. But even then, absent further information other than "It's dangerous", shouldn't one's approach err heavily on the side of caution until-unless one learns the degree of caution actually needed?
Much of the reason a house fire is more dangerous to you or I than to a trained firefighter is that you and I don't have either the training (a lot of which involves safety and caution) or the equipment (which largely revolves around safety) that they do. And even despite all that, every now and then we hear news reports of a firefighter badly hurt or even killed in the line of duty because something went wrong.
But a party of 3rd level adventurers DOES have the training and equipment to handle most naturally occurring threats. Again, this is the point. EVERYTHING the Adventurers do is "dangerous". Fighting bandits is dangerous, fighting goblins is dangerous, fighting diseased filled giant rats is dangerous. They start off 1st level being told "this is too dangerous for us townsfolk to do" and of course they are cautious at level 1. But by level 5 when told "this is too dangerous for us townsfolk to do" THEY PICTURE LEVEL 1 THREATS. And so, to the players, they hear that and they think "we handled something like this easily three levels ago, this shouldn't be anything to worry about."
That "absent further information" is the entire crux of what I keep trying to say. Just telling the party "this is dangerous" is meaningless. You may as well say "you will be adventuring on a Tuesday" or "This time water is wet". And yet time and time and time again, I've seen or heard about DMs flummoxed about why the party went to do something after being told it was "dangerous". Danger is relative and a meaningless term past level 3 unless you add context. You need to properly frame the threat so that the players get what you are trying to say.
Is it "This is dangerous" aka "you guys are going to have fun with this one" or is it "This is dangerous" aka "Guys, don't go this way, you will all die and you aren't ready."