Basically, you can place block inside your head by aiming fences. Fences are the only thing it will affect. It will not allow you to place blocks next to torches or ladders. You will suffocate yourself.
What I expected to happen?
You cannot place a block there.
What actually happened?
I suffocate from the block I placed.
1. Place 2 fences on top of each other or a fence on top of a block.
2. Change your gamemode to Survival while holding a block
3. Walk next to the fence
4. Aim the side of the fence that facing you
5. Right click to place the block
You will suffocate and will not be pushed away immediately.
This is definitely not a feature , since placing blocks inside yourself does not make sense.
My opinion is: when placing blocks with facing fences, you should detect if the player will be inside the block.
In the screenshot, both the left and right setup will have this issue.