When I first found out about limerence via Alan Robarge, I knew for sure that it's what I'm struggling with and relates to the childhood abandonment wound. In that regard it is pathological and extremely painful which makes it almost a form of self-harm. I think for me, holding onto the idea of a dead relationship from over 5 years ago is absolutely limerence and a psychological problem.
However, I'll say it again, I think a lot of what's being discussed here isn't.
During my recovery from substance addiction, I have attended 12 step meetings of Sex and Love Addicts Anonymous (SLAA). Now I am absolutely not a SLAA, so I never stuck around as I didn't relate to the stories being shared. A lot of what people spoke about at SLAA were having fantasies about work colleagues, daydreaming, having inappropriate crushes and even manipulating situations in the hope of getting with that person. I think a lot of what is being mentioned here is in that category and I suppose that being the case, then it's a form of escapism and fantasy that could turn into an addiction if one is out of touch with reality too much.
Also, there's human nature, people are flirty and do breach sexual boundaries. It is exciting and euphoric.
Speaking of euphoric I have also known people over the years who have bipolar / schizophrenia and when they're unwell become romantically or sexually fixated on someone who isn't really in their life like that. Even being sexually disinhibited. So there's that as well.
Plus there's just regular people who would really really badly like a loving relationship and it can get painful being alone so one can go a bit bonkers.
I don't know where exactly limerence lies in all of this by technical definition but I do related to the experts who say it's a trauma issue.