Mobs will look at you when you are in creative mode, but they won't make an effort to attack you, thankfully.
Linked issues
Comments 7
Also see MC-10901. Reducing this ticket to creative mode.
I'm 99% this is intended, since you can trade with villagers in creative mode, and villagers look at you when you are trading with them.
Why wouldn't they look at you, you are visible and can be toughed (but not harmed) I see no reason for this to change
The comment above by the Mod explains that it wasn't originally only this.
I think it should still be removed, as they should interact with the Survival players, not the creative. But it originally was for Invisibility Effect as well.
Erik Broes
This might be a part of this bug or might be intended or another bug, but Guardians do both see and attack when player is invisible. And yes, without holding anything in either hand or wearing any armour. Tried in 1.8.8 and there they don't attack, but in a fresh 15w51b world they do.