I often see one nickname on YouTube, and commentators write another. Where?

Question

YouTube

Wow! I don't know if anyone will understand. But, like in Russian. Often in YouTube, I observe a discrepancy between the displayed nicknames / names of some commenters, or even the authors of the video, with the nicknames / names indicated by the side of those who refer to them, other commenters, including during the transition (for my attempt to see these different ones indicated by them, -- nicknames/names) to the channels indicated, -- explicitly, according to the context of the messages, related to the same commenting users, or the authors of the video. Where and from where, other commenters see these different nicknames or names from those originally displayed?!

Answer 1

A person had one nickname, he wrote a comment, he was answered.
Then the person changed his nickname, and the old one remained in the answer.
Easiest.