[this Bug has been already on older Versions]

On most of the servers [Hive, CubeCraft, ...], there are some players which have for everybody the same skin. For example, when there is a player with a steve skin and a player with an alex skin: For the player with the steve skin, that player has steve skin. In perspective of the alex player, that player has an Alex skin.

PS: I don't know if the server causes this bug [On Hive, there are some entities which have your skin (Example: First three places on Death Run: your skin, but in Grey]