A troll is plainly no longer a surprise and it's doubtful they ever were.
I do think that the troll example, and monster traits in general, is not a good example to use, and I think it kind of distracts from the bigger problems of meta-gaming. Although I'm going to get back to monster traits in a bit.
Like I said above, if we really wanted to get into it, my view is much more nuanced than some flat ban on all meta-gaming. You can't do that, because you can never get rid of all kinds of meta-gaming. But there are some general concepts that I thought were widely accepted, but perhaps not.
But let's take something like knowledge of the campaign world. If I am running a Faerun campaign, and none of my players know anything about it, then the player knowledge might closely fit the character knowledge, if their characters don't know much more about the world than their immediate surroundings. So as they explore, I might have them make history checks when they learn more about the world, or they might learn things as they travel and research and adventure. And character knowledge pretty much parallels player knowledge.
But let's say one player is a virtual expert on the Forgotten Realms. There would be some pretty silly scenarios if that player had to constantly act like he knew nothing of the world. I think it makes more sense if that player plays a character who just does know more about the wider world for one reason or another. Ultimately it's up to him how he wants to create his character and what knowledge that character has. But this is an example of where there is some crossover, or bleedthrough, of player knowledge and character knowledge.
And I have no problems with that. These kinds of things are not big meta-game concerns I draw a hard line against, or any line against.
What I don't like though are meta-game playing that is inconsiderate to other players. Let's say that as all these new players encounter various unusual creatures, like lets' say a beholder, and say the one player who is a veteran D&D player blurts out right from the start, "stay away from his central eye, it's an anti-magic field."
Well, hold on, wait a minute, the other players didn't know that, and perhaps their characters didn't either. If there is a good reason that your character knows that bit of information, story and background-wise, then fine, no problem. But if you keep doing that for every single creature because the player just knows everything about every creature, isn't it kind of apparent how rude and inconsiderate that is to the other players who are role-playing and are learning about these creatures for the first time? And unless there is a good reason why that character is an expert on every single creature, then it is a meta-game issue, that is, again, an inconsiderate way to play.