Coltan Yakich

Sorry, was unaware the a report could be reopened.

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.

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

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}