Personally, honey is for me less an animal, because it’s an animal product

Jellyfish is an animal in itself

But to be honest, I’m a carnivore, so I’m just talking out of my ass and anyone else can probably give more educated answers

Edit: and as far as I understand, it’s not about mammals, it’s just if it lives.
For me the border is also hard to draw, because, as you say, plants communicate and seem to feel stress (which could be interpreted as pain)

It’s a personal thing anyway.

Edit 2: there are also grades of vegetarian/veganism
Like only eating fruits/nuts, that already dropped from the living plant. Which would probably the most strict and consistent philosophy.

But food is always also a psychological thing.
I went for raw vegan food for some time (until mandatory military killed my diet), and all my allergies were gone
But a friend of mine was starving on the same diet and looked like shit.
Everyone is different…