It is hard at times to play a game knowing what you know vs knowing what your character knows. Some find it easy others not so much.
Yes, this is one of the most difficult things to do. Would a low level character know what certain creatures are? Maybe not. But a player who played for years would and would know how to fight it even though his character wouldn't.
With consideration of this, I have many I've seen many people that have argued the summon monster spells or the polymorph spells are too powerful in Dungeons & Dragons but a detail in 1st least a few versions of these spells is actually having a knowledge of that what you want to transform into or summon.
It is with this that I as a Dungeon Master would never allow free access to the Monster Manual, are there character wants to transform into something or someone something that they would not reason would be even know existed or have much to tell about would probably require a couple of additional rolls.
Metagame knowledge of monsters can be especially a problem, since many players have read through the Monster Manuels at least once, so the idea a presenting a challenge that they as players wouldn't know how to overcome and pass onto their characters without the proper rolls or knowledge checks can be a problem.
Metagaming defeats the whole purpose of roleplaying to me. Heavily metagaming can easily turn a game into roll playing instead. People are so concerned with their character dying for example. It's part of life. I get attached to my characters but if they fall I move on. I try not to metagame at all. To me it is cheating. I'm not saying I haven't done it before. I just do my best not to.
I think everyone likes their characters and they hate to lose a character but yes it does happen in life and you move on. I try not to metagame and if I do I do not mean it too much. I would say most people do it now and then.
I'm with you two. It's definitely like losing a friend but in the end I can roll up a new friend pretty quickly and see where this new friend goes *wink*.
My main pet peeve is not roleplaying in the story. To illustrate what I mean picture a winter scene with a character has no blanket, no tent and nothing to start a fire but is ready to camp the night and move forward to the morning. Sorry, that won't work… we need to make some frost bite checks!