I see you edited so first i will respond first on that.
We're lucky enough that they even care enough to import of previous LI choices and have it actually be mentioned and reflected upon in game. That in itself is complicated enough. Leliana is the only DA LI that is part of the inquisition and probably the only DA LI we will regularly see enough to warrant the possibility of a full blown romance and why should they do that again when there are other aspects of her character to explore and there's a large chance she's already committed to the Warden anyway (as she was the most popular DA:O romance according to input data if I remember correctly)
The only way I really see this being conflicting is in the case of Isabela and Zevran. Zevran isn't going to show up but Isabela might, and/or not being able to propose a fling to her and seeing her say no if she wasn't romanced is going to be a bit weird...
Well i wouldn't call that lucky pretty much same as with ME romances got treatment as something major bioware practically have to put reference to romance from previous li even if it is done just stupid like in leliana cameo that was in da 2 but i will mention that later.
She isn't same person as she was in dao and when you romanced her last time , as i said she is after major changes that pretty much removed her many traits from dao.It is obvious that simple now even having her in your team will be different experience not only because she is your advisor because her character has changed so romancing her would be different than in dao. Of course im not saying that it is reason that she should be Li in dai im just saying that saying that she shouldn't be li in dai because she was already in dao isn't very good reason.
Now to go to part about where reason is "my pc romanced her previously s/he shouldn't be li in next game" is bad practice as well when devs start act characters out of character just to not ****** peoples because they thought that hedonist that have very lax view on relationship and sex wouldn't go to bed with another person... in fact i was glad they did that with romanced zevran until it turned out to be just bug.If they will turn isabela into chaste nun just because she romanced hawke i will be little disappointed with bioware.
He might have said that in one thread but they have many responses all over the place and there is not just "one" reason, obviously not pissing people off is a reason but it's not really fun to revisit old grounds.
Well you are right about reasons but i was more talking about that 1 specific and as i said it wouldn't be rly old grounds because she isn't same person as she was then.