I'll admit, I have been too busy to read Nishant's old posts up till now. But as I was just saying about it being the worst kind of malice/evil to look at the truth and just "not care"...
1. There is no way a person's speech patterns, writing patterns, will change drastically in just 10 years. Capitalizations, composition style, even spelling is not going to change that much in 10 years. If you look at my old posts, the only difference is that I used to sign my name at the bottom of each post. And MAYBE I had less words in ALL CAPS (for emphasis) in my writing. That would be a minor, organic habit or development. It has been over 15 years. But my posts from 2006 don't appear to be from a different person.
I know I can tell someone's posting style; I can almost identify people by it. I don't think I can quite program a computer to do so -- but I bet I could program a computer to look at different metrics, and form a sort of unique "fingerprint" with a % chance they are the same. That much is possible. Looking at total vocabulary, favorite words, spelling errors per 1000 words, capitalization patterns, etc.
2. Those old Nishant posts (speaking from vague memory here, and that memory was refreshed by the OP) seemed to be from an adult -- a middle-aged adult. And said adult wasn't even part Choleric, as far as I can recall. How could he turn into the young, feisty, sometimes rude, choleric, naive "Nishant Xavier" persona? One's basic Temperament(s) do not change AT ALL over a lifetime. Choleric, Melancholic, Sanguine, Phlegmatic. Most people are a combination of 2 of these temperaments.
3. I never received the slightest proof that they are the same person. I took "XavierSem" at his word, when he claimed to be the same person. I gave him all Nishant's reputation and banned (closed) that account. I haven't heard from Nishant in forever. Maybe he died? Maybe since they're both in India, XavierSem had inside info that Nishant wouldn't be back looking for that account? At any rate, we still have no explanation, not even an official one, as to why XavierSem started that "new" account in the first place if he was Nishant and always was Nishant. It's not like he needed to escape a bad reputation or something! Quite the contrary. In all my years running CathInfo, I've never had someone "start over" with a new account and beg for their reputation from their old account to be brought over. I've had the opposite happen many times (people wanting a clean slate) but never the contrary.