Here are some examples with the latest development branch, vanilla, and the latest stable...

Looks like some kind of rendering error... It only applies to my armor and cape, my skin is opaque.

this is caused by a mod that alters the third person view of the player. i cannot fix this.

hey, @X0nk, I also have this issue, and I was wondering, do you know what kind of "mods that alters the third person view of the player" causes this to happen, so I could delete the mod and fix the problem?
Thanks,
William

shoulder surfing reloaded is a common one