They keep talking about their work on various things...
Nobody ever acknowledges them.
I try to sometimes, because I want them to be happy, but I'm personally not interested.
Do they just accept that nobody is interested and enjoy discussing anyway? That sounds nice.
Are they desperate? That's really sad.
I think they did the same before I'd left too.
It's because they don't actually know what they're talking about. At least, not really. They've done some reading but not really anything useful or understanding.
It's unrelated and I think they know it. It comes off as bragging... an "acknowledge me." If someone that actually cared about those things talked to them, they'd be forced to make shallow and general statements in order to maintain a knowledgeable appearance.
But it wouldn't be meaningful.
I think I know who this is. The obsessiveness of you personality is very hard to deal with, and is very childish. Also, you claim several people are lying about their age, yet at the same time you have contradicted yourself when it comes to your own age.