I read some of the posts by Majoru about his metagaming 4th ed player and it reminds me of a campaign I played last year where two of the players were so used to playing D&D as it was expected of them in 4e modules, that they didn't realize D&D could be played another way. Metagaming is explicitly banned at my table and it is bad form to even try to use it covertly, forget about using "I open the lock using arcana" type arguments. To be fair, 4th edition adventures were designed that way, so it's not unexpected for people only accustomed to that game to try to keep playing that way in a non-4e game. I would start off with a quick explanation of what metagaming is, what it isn't, why it's bad for the game and for player immersion, and if that doesn't work I would start doling out XP rewards or penalties or inspiration points for going through an entire session without metagaming. Maybe begin with that. A carrot is nicer than a stick. But eventually I'm sorry to say, a stick might be required. In our case, the 4e player was simply not happy playing 5e with totally different base assumptions about what the essential nature of roleplaying is for many people, and he quit out of frustration with the DM who would sometimes suppress player abilities if they did not seem possible to pull off or work at all.
It's a question of player entitlement versus DM entitlement. Metagaming is player entitlement run amock, but it's part of a larger issue which is, do the rules matter more or does the DM's fiat matter more? I waver on exactly where that line is, I much prefer to play by RAW most of the time as I think DMs have plenty of tools at their disposal even within the confines of strict RAW playing to make rulings, and besides that many DMs aren't very good at making effective house rules and sometimes their rulings stink too. I actually agreed some of the time with the 4e player who didn't like arbitrarily having his abilities not work, but that was more a question that I felt the circumstances didn't call for such a heavy handed ruling. And sometimes it's better for a DM to tell a player what the scenario looks like in mechanical terms like "you won't be able to try and hide in this room anywhere, it's too bright and there's no cover", or you can't use a polearm in this narrow 5 foot corridor to make an attack with the butt end of the weapon when the enemies are only in front of you. There are plenty of logical places to make rulings, but player entitlement is often founded on powergaming at the expense of good faith interpretation of the scenario at hand, and DM fiat is one of the cornerstones of this edition.
Most people are very happy with 5th edition as a result of this sea change in mentality. RAW plays plenty well in 5th ed without being heavy handed in rulings most of the time. Many times DMs have had to bypass RAW to overcome unbalances in the rules or player abilities, and it's great that they don't have to do that as much in this edition to make an adventure not be a cakewalk for PCs. That's just as bad as an unwinnable adventure.
It's really a question of maturity, if players are used to playing videogames with exploitable rules and getting away with it, and bringing that to a table with a human DM who will invariably get annoyed at this type of antic, then that player is probably going to create issues beyond that when they don't get their way or if their character dies. I just don't play with such people. The first question I ask new players is, do you expect DMs to fudge rolls to prevent your PC from dying due to combat? If the answer is yes, I don't want them. I have better things to do than fudge dice rolls to protect people's precious 5 minutes they took to write up their character. If you spend a huge amount of time writing a backstory for a first level character and they get smoked in the first session, that's too bad. Lesson learned. Make a new character, and don't waste so much time filling in blanks that might never come up.
