I mean depending on the DM they can be as bad as saying that someone with a str score one point lower is inferior to you. Not really 4th wall breaking when people do this in real life. MMA fighters, martial artists, boxers size up there opinionate all the time. And I mean PC know their own stats why wouldn't they have some idea that maybe the dude walking around in full plate mail maybe stronger then them, this just gives them an idea how much stronger.
I don't disagree with this, but this isn't what the ability says it does. It says you learn the relative value of the stats listed there. And you get to pick which one. This means your character explicitly understands stats exist, and that those listed there have some concrete metric.
Man that guy over there is carring himself with ease in that full armor while I have issues wearing my chain mail all day. - superior str
Man did you see that women dodge the bar maid so the maid didnt spilled the drinks they were carrying. If that was me I would have been able to catch the tray and prevent the drinks from spilling. - Equal dex or superior AC
Man that guy can hold his liquor he drinks like a dwarf.. Me I would be two ales in and need a bed for the night - Inferior con
Man I haven't seen someone move like that since my master taught me back in training - Superior fighter lvl
None of these things are 4th wall breaking.
You're right, none of that is 4th wall breaking but none of that is what the ability does. These are just casual observations anyone can make.
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Your L7+ Battle master knows that Strength, dexterity, constitution, AC, HP, Levels, and fighter levels all exist. And he knows they have some objective metric that he personally has learned how to get those relative values for by simply observing a target.
Again, your fighter doesn't learn "that guy over there is carring himself with ease in that full armor while I have issues wearing my chain mail all day" he learns if he has a superior "strength score".
It is metagame because you literally are learning the stats of creatures. Relative value only, but even just knowing of the existence of the stats alone is metagame. The characters shouldn't know that levels exist, or HP, or AC etc. Yes, they should know that people have various degree of experience (ie levels) or some would be harder or easier to strike in combat (AC) etc etc. But that isn't what this ability says it does. Your character picks two of those stats, and your character learns their relative value compared to his own. That's absolutely 4th wall breaking.
Arguably it can be fine if creatures within a system pursue potentially attainable knowledge about how their system works.
In our system scientists (people working by the scientific method) may seek to measure anything that can be measured. For instance, measurements might be taken on the rate of falling to find that at Earth's surface the acceleration of gravity is about 9.8 metres (32 feet) per second per second.
In a 5e world, intelligent characters perhaps with proficiency in investigation might come to equally correct conclusions but as fitting their 5e world.
Darwin wrote at length about pigeons and earthworms. Surely someone from Waterdeep or a similar location has written a book on fantastic beasts and where to find them. They might even colloquially name such a tome a Monster Manual.
You've got a group of varyingly perceptive characters. You gain experience and suddenly you gain things like an extra hit dice and become harder to kill. Surely someone might be able to notice the way things work in the world they live in?
It's fine for Charles Xavier and Moira McTaggart to study mutants and gather relevant knowledge. That's their world.
Similarly, 5e characters can remain comfortably within the three walls within their system while still gaining good understandings of how their system works.
Arguably it can be fine if creatures within a system pursue potentially attainable knowledge about how their system works.
In our system scientists (people working by the scientific method) may seek to measure anything that can be measured. For instance, measurements might be taken on the rate of falling to find that at Earth's surface the acceleration of gravity is about 9.8 metres (32 feet) per second per second.
In a 5e world, intelligent characters perhaps with proficiency in investigation might come to equally correct conclusions but as fitting their 5e world.
Darwin wrote at length about pigeons and earthworms. Surely someone from Waterdeep or a similar location has written a book on fantastic beasts and where to find them. They might even colloquially name such a tome a Monster Manual.
You've got a group of varyingly perceptive characters. You gain experience and suddenly you gain things like an extra hit dice and become harder to kill. Surely someone might be able to notice the way things work in the world they live in?
It's fine for Charles Xavier and Moira McTaggart to study mutants and gather relevant knowledge. That's their world.
Similarly, 5e characters can remain comfortably within the three walls within their system while still gaining good understandings of how their system works.