Is it okay to use another player's character 'fantasia' as your own without asking?

[Bixillarla]

What are you asking? How does one even use someone else fantasia? even if we account for logging in their account it is not tradable.

What they mean is seeing someone with a look they like then using that same look for thier character. They don't mean actually using someone else's Fantasia vial.

I don't think there is anything wrong with it.