What are the differences here?

[Sirius]

No, Charura was saying this particular marker couldn't be found in other Shards. She probably knows how to enable GZ marker quests
This marker was not accessible in Complete Chronicles...

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...since the Tiwah was the reward for re-enabling the GZ.

But this marker was buggy in a few versions of the game... The marker was here, but you couldn't click it. I think Deep Island disables it, MOUL might as well.
But it should be working fine in Gehn.

[Acorn]

The answer to your main question is that there are two "new" areas on the Gehn Shard called Tre'bivdil and Vothol Gallery. Both are very nice ages but not as expansive or as interactive as most of Cyan's ages that were part of the original Uru. There are also fixes for many issues that plague Cyan's MO:ULagain Shard and various technical improvements as well. We plan on adding more ages and technical improvements in the future, of course.

I mentioned updating the "welcome" and you thought it was a good idea, but maybe you thought I meant the Ki message, which I see you did update? Whereas I was meaning the "welcome" thread/announcement on this very forum. I know you've been tremendously busy so how about, as an interim measure, posting this reply (above) into the "welcome" announcement in the forum http://forum.guildofwriters.org/viewtopic.php?f=117&t=5540 so it doesn't get lost? It's the sort of info I was suggesting new visitors to the forum might want to know.