Yeah, let's just make sure we have our terminology straight, as it's different across many online games.
Server- this normally refers to a physical piece of hardware with inherent limitations on the amount of processes and memory it can run. It is also frequently used to describe the playspace that a fixed number of users have characters on, and characters on one server aren't able to interact with characters on another server. Developers would normally refer to the latter definition as a shard. Also, the term server for physical piece of hardware doesn't apply to the herocloud since our hardware scales beyond physical boxes to grow to whatever size a game requires.
Shard - a world or universe with a fixed amount of characters on it. WoW has dozens of shards. Eve Online is shardless and all characters play in the same space.
Area - in the heroengine this is a unit of server simulation, it roughly maps to an area of terrain and gameplay. Attempting to overwhelm a single area with too many assets or terrain or units of simulation (ai, players, etc) creates negative effects on the server or the users clients. Area can be stitched together with seamless technology to create the appearance of a game world that is expansive and epic without having to load assets when the player crosses an area.
So areas and shards and therefore world or universe are independent concepts. The discussions you've obsevered are about how to limit memory usage on the server, while attempting to explain to developers new to online world building that attempting to simulate miles of real world ocean is a common mistake and a waste of resources, but that in no way prohibits you from doing so.
Posted from my iPhone. Ignore all typos.
"I can do whatever I want and get away with it, because HeroEngine can adapt" is the bottomline?

After you have explained the views on terminology, I can now ask my questions better, and also give some more explanations:
Basically, the endgoal is to have a game in which all players play in the same world. As the player-base extends, new servers can be created, but there is not and must not be interaction between the servers.
I meant with "area" a part of the whole world, as explained here:
http://hewiki.heroengine.com/wiki/Area . It's not our idea to have "miles of sea" all the time, but there are a few, I can think of 2 now, cases in which it is needed.
In the end, there is nothing that stops us from stiching together a lot of areas. Re-reading the updated wiki pages has increased my understanding.
Thank you for your replies!