Oh I didn't know this was a rewatch haha. I started browsing the last pages of this thread because of the recent off-topic thread and I wanted to see people's reaction to Bisky's English dub voice in the latest episode.
I didn't really notice the similarities until I saw how Gon got badly damaged in the Chairman arc. But even then I was more worried about the power of Killua's sister and enjoying Hisoka and Illumi's schemes.
Agreed on the going super. In a lot of ways, the way the animators did the crazy black lines reminds me of the scene in Ghibli's Princess Kaguya when the main character gets upset and angry before she runs away from home. Her negative emotions get so strong that eventually world around her just became abstract lines with shades of only black and white. Of course that's the animator's depiction of what she feels and what they want the audience to see but the message is still sent. Here's a clip of the scene:
https://www.youtube.com/watch?v=Jtc-PP2GWPo
Edit: Oh forgot to write more about the power up. I draw the comparison to Kaguya because of how the animators in both show and movie drew simple but meaningful black lines so appropriately. But what I liked in Hunter X Hunter was how aggressive but also frightening pure blackness can look like when it goes out of controlled.