Here's something that was in the Jackolyte thread.
"Well, I think that one of the reasons that the breakups by and large are so easy is because BioWare was still dealing with the post-Horizon fallout as well as people complaining about ninja-mancing. So I guess they just wanted it to be like yanking off a band-aid. I think it works for Jack because, as I said, she's has grown as a person and I think it compliments the interpersonal work that Shepard did with her. Jack wants you there, but she doesn't NEED you there. She's not "fixed," per se, but then again, who among us really is?
And another reason I think it works for Jack in particular is what happens when you contrast her with her old arch-rival Miranda. After the two of them butted heads all throughout ME2, they kind of rubbed off on each other about as much as Shepard could rub off on either one of them. In Mass Effect 2, Jack was solitary and lonely with no one to prop her up and she had nothing to feed on but her own rage. Miranda, on the other hand, was so desperate for someone--ANYONE--to accept her for who she was (after dealing with her father, who wouldn't) that she places herself unquestioningly in the hands anyone who won't try to change her.
Mass Effect 3 rolls around and the roles are reversed. Jack found meaning in something greater than herself and acceptance in a kind of mother-hen role for an impromptu family of biotic kids. Miranda, meanwhile, has started trusting herself a little more and is now acting with agency, tracking down a lost sister and getting her revenge on all by herself. Now dump them. Jack, who knows she's good enough finally and at long last and doesn't need Shepard to tell her so anymore, plays it off. Miranda, who at that point has no one else in her life other than you, completely collapses.
I think Jack and Miranda have the most fascinating character dynamic in the entire trilogy. So while some of us want Jack DLC, and some of us want Miranda DLC, I want Jack AND Miranda DLC. I want to know what these two think of each other before endgame.
Wow. I started on one thing and moved on to something else entirely. I'll shut up now."