As my last Report was closed prematurely for an unknown reason to me.

With the command [Mod]Kumasasa gave

 /summon ArmorStand ~20 ~1 ~ {Invulnerable:true,Invisible:true,Marker:true,CustomName:"I'm a Marker",CustomNameVisible:true}

While almost the same effect, all it does is make the summoned ArmorStand invisible(Use Gamemode 3 to see). While you cannot "see" the ArmorStand it is still 'rendered' Including any items ON the ArmorStand regardless of what Invisible is set to. While with how Marker is defined(and from what people have said on various threads/shown on YouTube. Marker stops the ArmorStand or anything equipped from being rendered. This is important because it can reduce lag significantly when large amounts of ArmorStands are used in a map.

According to the Wiki(Link Below*) Marker was defined as

Marker: (1.8.1-pre) - 1 or 0 (true/false) - if true, ArmorStand's size will be set to 0, have a tiny hitbox and disable interactions with it. May not exist.

Using this command

summon ArmorStand ~ ~1 ~ {CustomName:Demo,CustomNameVisible:true,Marker:true,Equipment:[{},{},{},{},{id:"leather_helmet",Count:1b}]}

Demonstrates the bug. The ArmorStand's name simply moves to where the new hitbox is(which is the tiny size 0 hitbox).

Wiki Ref. - http://minecraft.gamepedia.com/Chunk_format#Block_entity_format
Youtube Ref. - https://www.youtube.com/watch?v=Vgc_tZ2GHvg

The reason people use the Invisible tag is so that when it is rendered by the client(not when summoned) the ArmorStand is not visible for a single tick.