Huh. I find it curious how differently one thing may be interpreted. Xenogears' vagueness on a number of important topics and just general incomplete state certainly don't help any, but still.
Seeing as how I am a fresh blood and didn't see any sidematerial, fanfics and forum speculations before today, I'd like to share my perspective in hopes anyone finds it interesting.
These points from kare's post:
...It's hard to get answer on that topic since both Grahf and Elly are not longer Lacan and Sophia.
Let's start from Elly and Sophia. We know that both of them are reincarnation of one soul. Let's remember that each Elly reincarnation lived own life, their characters may be different a little since they lived in different eras, families etc. Core of soul was the same, but we can see that Sophia was different too, see color of her hair.
Elly wouldn't ever become like Sophia since she has her own life, and even if she'd remember her past selfs then it won't change so much who she was in her life.
Elly never spend time with Lacan, she would never become Sophia...
I believe I've got the complete opposite impression in regards to Elly from the game. In my opinion, all Elly's reincarnations we were shown were quite similar to each other - almost eerily so. And further the plot progressed, more and more like Sophia the current Elly became. That universal care for wellbeing of everyone but herself to the point of suicidal behaviour? That is nothing
like the Elly we see in the beginning.
Now as for 'Fei'... Every 'Fei' we are shown are clearly different people beyond the unreal similarities in physical appearance, access to experiences all the previous 'Fei' lived through and strange propensity to repeatedly find themselves in the company of current generation's Elly (with about the same age gap each time too). In all shown cases they appear close to each other, in a sexual manner in some of them, but 'Fei' himself is different each time. Furthermore, after he sees what some of the previous 'Fei' were up to, he does not become more similar to any of them. He is not completely unchanged, but nowhere near what Elly goes through.
So, to Lacan - someone who at the time the game happens has already had a talk with whatever resides in the Zohar and at least has an inkling of a clue about what is happening - current Elly as she was when he meets her for the first time may have been less objectionable when compared to Elly behaving more and more like Sophia.
I don't find it difficult to imagine that seeing the proof of the woman he loved feeling anything at all for him only because some machine has instilled a directive to respond to 'Fei' in such a manner ages ago (if what Krelian and Miyang-Karen talk about is to be assumed the norm for the whole duration of events, Elly may not be even born before the next 'Fei' does) with his own eyes - seeing the proof of Sophia being nothing more than a function
in this circus of misery since she was born and to the moment of her death - may have ignited hatred so strong that it makes Id's destructive impulses seem like a temper tantrum in comparison.
I find it reasonable to assume that Lacan's feelings for Sophia had not faded. They may have changed in nature, but the intensity has not lessened. It grew more and more, if anything. Remember: Lacan is the one character that values his own life less than even Sophia does. He would not have kept doing what he did for as long as he did if he was only concerned with his own wellbing, only his pain and suffering. IMHO, if that were the case, he would have long since killed himself. The next 'Fei' would be some other man with his face and maybe some of his memories. Lacan himself would no longer exist and thus will feel pain no more.
Elly on the other hand... Elly will continue to be dragged around this mockery of life for years and years to come, compelled to conform to that one template as soon she meets 'Fei', effectively erasing whatever person she may have grown up as until the point of no return is met again.
Now this would be a plausible reason for Lacan to want to erase this whole joint, wouldn't it? So no, neither Lacan's love nor his sanity has not gone anywhere, methinks. He just stopped caring for anything besides freeing the woman he loved from this fate.
This is full of headcanon of course, but it seems a likely explanation to what was shown in the game to me, so I wanted to share it with you.