So I found the concept sketch of the Sovereign's separation lines, but I can't find shots of the actual, final model's separation ability. Anybody have pictures of it?

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So no.

Actually nothing there saying the ship can't saucer separate....and there's been no word of god on if it can or not.

Considering that saucer seperation has been a feature that been considered for the Enterprise since the original 1701, I'd say that every 1701 Enterprise since that ship (and any other ships of their class) have been capable of saucer seperation. It's only the 1701-D that we've ever seen actually seperate (a grand total of 4 times).

Granted...in some references...The old Starship and Connie classes...the saucer is not capable of reconnecting on it's own....Supposedly according to those references...The Galaxy was the first class capable of doing that. All others could only be reconnected at a spacedock facility.

Granted...this was information I found back in the late 80s after TNG had already premiered (holy crap...it just hit me how old TNG really is......) from a Tech manual or something...

Actually It was made prety clear in "mission farpoint" that the Galaxy class was the first ship with that feature...

About the Souvereign beeing able....
Well in non-canon novels it was said she can....
... the concept says she can (wich as close to beeing canon as you can be without beeing canon IMO )
Also... I think the model itsself screams "saucer sepparation" all along...
So I'd say its reasonable to asume she can.... but Canon itsself never said that (since that ship had only 3 appearences - not a big suprise that there are little canon facts...).
Canon does not say if there is a John Miller living on earth.... but considering how standard the name is its reasonable that amomg the earth population in Star Trek there is a person with that name.

An argument against that, on the other hand, might be simply: The Galaxys saucer sepperation was build to give Families and civilians a large scaled escape vellel while the engeniering section fights....
Well the Souvereign/ Enterprise E does not seem to have many families and civilians on board.
But the Promethues sepperation was build with other tasks in mind... too.

The "E" was one of the many Enterprises to not be able to separate, only the Enterprise 1701 / A, and D...well I think F now, can saucer sep. The rest had 1 hull.

Depends on what reference you use.

Some say that most Federation cruisers can Saucer Sep....just not all of them can be re-attached without spacedock facilities.

Some say that it was ONLY a class feature of the Galaxy, and no other.

Some say it's only a feature of the Enterprise and no other ships...regardless of class...

If you are so sure about that you have a canon source arround?

If you dont... then neither her ability to sepperate nor the lack of that ability is canon.

The only thing you can say that IS Canon about the SOvvie's separation ability...is that it never happened....at least never happened on-screen.