I see different interpretations of this all the time; a player is killed for passing or not iding a body, however, there is no way for them to have seen it from where they were. I've seen players get slain for this, and players not slain for this, and it is very inconsistent at this point and needs answering. When a player, from no matter what angle they are at, cannot see an un id, or even know of an un id, should they be killed, or not?
Consider it as a 360° Line of Sight determination. If a body is somewhere in a players 360 LoS and they make no attempt to get to that body and ID it, they can be killed. Exceptions to this are if it is physically impossible for the player to get to like places where they could take damage or outside of the map.
It very much does matter what angle they are at, and where the unided body is. The rules state that the player cannot be killed for an unided body that they aren't able to see. However, this does not mean that just because you didnt see the body on your way there that you can't be killed for it. This rule only protects the player from unided body that have physical limitations to be seen (i.e a wall or a door). If it's just lying around and you miss it, you can still be killed for it. This rule is meant to protect against abuse from other players and planting/killing for acts that the other player had no chance of responding to. For a deeper discussion, visit here.
As frustrating as it is getting killed over not seeing and un id body, I think it's a fair rule. Player A has no way of knowing if Player B actually saw the body and ignored it or didn't actually see it so he(A) has no other option but to kill him(B).
To give a recent example, if a body were hidden in a closet, and a leg were sticking out of it, and I passed that same room going in a way that would not allow me to see the body unless I went right up to the aforementioned closet, is that permissible to kill for?
This would really just depend on how visible the body is from the closet. If it's something that you would generally notice then yes the kill is fine. If it's just a small part of the body sticking out and hard to see unless you get real close, then no don't kill for that.
Perhaps this should be clarified in the !motd, and have deeper investigations as the situation varies between each staff member I notice (which is justifiable). Some are slain, some aren't, and nobody knows what is going on with the un id scenarios.
I have been in a situation like this and saw many players in situation with UnID bodies. Here is the "Not identifying bodies" Rule list Let's give some examples. A) Player Pacfist was running away from a c4 that he was telling in the microphone which is in a specific location. Let's say Pacifist was passing an UnID which was near a C4 about to go off. Player's cannot kill pacifist since he was in immediate danger or as it would cause harm/death to him. B) An Unidentified body was spotted by a Onlooker who was 20 meters away from the body which is in "Room A". Pacifist was doing his usual jogging down the hallway that has a room 90 degree angel where the "Room A" hold a UnID body. If Pacifist has his back turn to this, he shouldn't be slain since he did not see the body as it was in a different room. B1) If the Unidentified body was in the hallway where pacifist was jogging and pass over it, he can be killed for it as he was witnessed passing over an UnID body. B2) If the Unidentified body was just peeking out enough for Pacifist to see, while the Onlooker was staring at pacifist for him to noticed the UnID body. Pacifist has to check the body as he witness the UnID body just creeping in "Room A" otherwise onlooker has the right to kill him. Many variables can make up on witness and seeing and what not has been seen is greatly taken into account when moderators review the death scene. C) If I myself happen to see a guy running down a hallway with multiple doors. I turn around the corner and see an UnID body I should be able to kill him BUT if I don't happen to see him pass over the Unidentified body as the Unidentified body could have been killed right behind him which I didn't witness NOR he hasn't "seen" is possible as well. I have no right to kill him. I hope these examples are good enough to understand and answer your question.