ArmorStand Marker:1 tag still renders armorstand & anything equiped

Marker is a boolean -->

/summon ArmorStand ~ ~ ~ {Invulnerable:true,Invisible:true,Marker:true}

_{Edit
Edit2 Source}

This is how it was summoned, I failed to document as such on the sign. I tried both capital & lower M just in case as well.(resulted in same thing)
Exact command

summon ArmorStand ~ ~ ~ {Marker:1b}

Have edited my comment, see changed tags.

It still failed to NOT render on a newly generated world, as well as a world generated pre-anvil format then converted.

https://imageshack.com/i/ex6UoJxtp

Of course you need to set CustomName and CustomNameVisible, thought that was known...

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

With the command you gave ,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 simply turns black as if it was in an area with a 0 light level.

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

P.S.
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.

The Marker tag is not supposed to make armor stands invisible, the Invisible tag has to be set as well to achieve that. Equipment on armor stands should always render.