Plenty of systems have something for that, often with a variety of options.

A bookish Exalted character might roll Intelligence + Lore to remember having learned about the weakness to fire before. Or maybe Intelligence + Occult if the weakness is supernatural in nature. A combat-oriented character might roll Wits + War to deduce that fire is needed based on the knowledge of old battle reports involving trolls. Maybe even something involving Survival if they’re familiar with a region trolls can appear in.

A game with a flexible skill system has a lot of room for such things.

Oh, sure, you could absolutely make a case for your character accidentally stumbling on the right answer simply because fire is a good weapon, and a good roleplayer could use that to their advantage to metagame a bit more acceptably, but there’s a difference between that and just automatically grabbing fire stuff because you the player know it’s good against trolls.

Plenty of systems have something for that, often with a variety of options.

I believe 5e has a similar rule, but it seems rare for players to have actually read the rules. I don’t think D&D is especially detailed about this, but I don’t know where the book is to check. I don’t think they give DCs, where I wouldn’t be surprised if Pathfinder 2e had a simple “target number is 8 + the creature’s HD” formula with guidance on what to do for the range of possible outcomes.

Like I think stealth rolls should be hidden. You shouldn’t have an idea that you’re not hiding well.

I don’t have the players actually make the stealth roll until something opposes it. They’re doing the best they can. Here comes the guard. Roll, please.

I’ll take a meta gamer over someone with “my guy” syndrome any day. At least they’ll progress the plot.

My guy syndrome?

Iirc it’s a level DC based off of the monsters level

Some people just like rolling up new PCs ‍️

Without looking it up, I’m fairly certain that Arcana, Nature, and maybe even Survival checks can all be employed to fill this “character knowledge” confirmation, and have always been used for this and more. ‍️

Ah, okay then. Hadn’t seen it in that phrasing before. Pretty stupid as an idea though. The issue is not that someone wants to follow diagetic character motivations, or even that someone else wants to play with a focus on successful combat encounters regardless of diagetic knowledge. It’s that they both ended up at the same table. The DM fucked up by not setting expectations regarding the kind of table they were running. It is our duty as organizers of play to prevent these kinds of people from playing different games at the same table.

slightly neurotic diviner who almost always knows what’s optimal, and struggles between doing the obviously ideal thing or rejecting that and knowingly doing something suboptimal so they aren’t just a puppet to the magic

please tell me they experience different flavours from gems, like they’re candy, but the other party members keep trying to taste gems and it’s always just flavourless crystal.

and every now and then your sorcerer meets someone who shares their baffling ability to use gems as infinite gobstoppers, and they start enthusiastically chatting about what materials and cuts are best, as everyone else just looks on in confusion and exasperation

That’s how I did it when I DMed. On the off chance they need to make a check and I don’t want to alert them I just use passive or roll for them.

Yeah, this is the way.

We just fought a Troll in a Pathfinder session I was in. I’m playing an Athamaru (fish person) new to dry land, so I don’t have a ton of knowledge about stuff like fire. But the Druid hitting it with a fire spell, and the GM describing the way the Troll reacts is enough to naturally gain that knowledge on the spot. There are all kinds of reasons a character might not know even common monster weaknesses.

I think doing this kind of metagaming is important, because it gives opportunities for specific characters to stand out. If you have a party member with monster knowledge, it’s cooler for them to yell a warning, than it is for everyone to just act like they already know

It’s not just the GM’s responsibility. All the players at the table should be having those discussions throughout play

You have other people to manage wildlife, often times, and are probably not likely to encounter said animals. If you are then you know to carry bear spray, for example.

Now imagine you’re in a world where bandits on the road are threat you actually have to consider. Trolls might live down the road and your town sends out memos saying “if you see these signs, run, and if you absolutely must then fire is the only thing that will be effective.” It’s perfectly plausible, you just need to be the littlest bit creative/steal stuff like wildlife advisories from the real world.

You don’t even need an NPC. My first character was a sorceror who didn’t know what he could cast but his will, muscle-memory, and being in certain situations brought it out of him. Any “puzzle fight” should have enough room for players/characters to realize there’s a problem and the discover the solution. You can’t plan ahead, maybe, but there’s no reason you can’t have one roleplay turn and then “get lucky” choosing a fire spell next to see what happens.

Tip for shy/annoying/cowardly/etc. characters is to make it a thing they overcome. My current character is just a lil’ guy who basically got possessed so he’s constantly scared shitless but he’s trying his best and I’m always on the lookout for opportunities to get him out of his shell or even just to feel like he has to say something whether he likes it or not.

Ok, I’ll throw my hat in the ring.

Metagaming is fine, actually.

Obviously, don’t read the module you’re a player in, but knowing to use fire on trolls is just basic game knowledge. It’s ok to be good at the game, because it is a game. If you’re playing dungeons and dragons, or pathfinder, or any other rpg that spends most of the pages on combat rules, then you’re playing a tactics game. I like tactics games (I’m not good at them, but that’s a separate conversation).

I cannot tell you how frustrating it is to come up with a brilliant plan to do a thing, and then be told that I’m not allowed to do it because me figuring out the puzzle is metaknowlede.

It is exclusively in the tabletop rpg space that being good at the game is considered a bad thing. It’s in a similar vein that I hate tutorials in video games, especially when I’m being prevented from doing things that I already know how to do (because I’ve been playing games for multiple decades now and I have some amount of media literacy) for no other reason than the game hasn’t taught me yet. So arbitrarily, I’m not allowed to use fire damage on the trolls until some npc tells me that trolls are weak to fire? That’s asinine.

If you want to play let’s pretend with dice, that’s fine. just be honest about the kind of game that you’re running from the get go so I know not to join your table.

Eh, I know nothing about how to handle most dangerous animals, even ones that live in my area; I’d imagine that even in a world with trolls, regular people wouldn’t know anything about them.

Debatable. You definitely know a Tigers greatest weakness, and a bears greatest weakness even if you don’t know how to use them. >!Bullets!<