Wikipedia states that "metagaming is any strategy, action or method used in a game which transcends a prescribed ruleset, uses external factors to affect the game, or goes beyond the supposed limits or environment set by the game. It can also refer to the game universe outside of the game itself." Asking a player only for their role is not considered metagaming, but is part of normal gameplay.
In Town of Salem, metagaming is most commonly used to help a Town member prove their role and hinder anyone else from claiming to be a Town member. The player is asked to type out the exact text for the abilities, attributes or goal on their role card, which are unique for each role. If a player is lying about their role and is unfamiliar with the description of the role they have claimed, they will be unable to respond immediately (Or at least many metagamers believe, though in practice, a good player can be quick about it), or refuse to paste their will, and become highly suspicious to the Town.
In practice, metagaming is used in different situations:
- The Jailor may ask their prisoner to type the text on their role card. If they refuse, take too much time, or respond incorrectly, the Jailor could execute them or at least leave a note about the prisoner in their last will.
- The Town may ask a suspicious player to type the text on their role card during the day. If the player fails to do so, they may be lynched on the same day, investigated, or role blocked.
- A Mafia or Neutral player may call out a Town member during the day, asking them to prove their role by typing the text on their role card. If they fail to do so for any reason, it can be used to direct suspicion or even lynch the player. This happens rarely.
Metagaming is frowned upon by the staff of Town of Salem and also frowned upon by a large portion of the community. The exact text of the role cards is accessible online (e.g. on this wiki) or can be prepared in advance. As of Version 2.0.0, players can also view role cards during gameplay. The player may click on the name of a role or faction in the role list to find more information. Experienced players may know the exact content of every role card by heart. Despite that, metagaming is not against the rules, despite the thinking it should be.
The main problem of metagaming is its ineffectiveness. In essence posting attributes is nothing more than an excessively cumbersome method of claiming a role. Anyone can post them (especially after Version 2.0.0), just as anyone can claim anything in chat. Furthermore most players DO frown on meta-gaming and as such will refuse to cooperate with the one asking for role card text. Thus resulting in excessive unfounded suspicion that most of the time leads to mis-lynches/mis-executions, lynch wars between townies, and even convenient excuses for game throwing.
It is worth noting that posting of wills is NOT meta-gaming.
Wills are supposed to contain in-game information and refusal to share it is equal to refusal to co-operate with town.
There's nothing wrong with hiding some of that information to keep the known town roles hidden from mafia, but generally speaking a town member that has revealed his role has no reason not to reveal his will as well. (In fact, any claim that's supposed to have a will but was not immediately followed by it is either an indication of evil or a part of being/faking jester, or, much less likely, a sign of a very bad player)
On top of that, since all the willed information has to be acquired in-game via the means available to the given role, information in wills can be used to legitimately strengthen or weaken the claim's validity. Wills can be both cross-referenced (example, you see a LO will that should have listed you as a visitor, but doesn't, or a BG will that lists a target that was jailed on that day but doesn't actually SAY that it was jailed) and checked for logical misbehavior (example, you see a LO/TP will that ignored a resurrected town member, or an escort claim that didn't switch targets to keep searching for a mafia killing role when there is only one MK left). And both of those practices are legitimate parts of the game.