Flamestrike
Legend
The difference is being hidden with hard cover (like a pillar) and being hidden with heavy concealment (e.g. Darkness). Sulked doesn't help with popping out either since you have to leave hiding to attack.
The basic question is does popping out count as revealing yourself. If you say no then you would have to allow someone hidden behind a pillar or wall you pop out, not attack, and stay hidden.
Yes I have no problem with a hidden creature behind pillar, tree or around a corner or similar obstacle observing someone in the room and remaining hidden.
The advantage you gain on the attack from being hidden is the sudden attack from a person you didn't know was there or from a direction you didn't expect.
If you broke your cover and just stood there like a grinning idiot for several seconds I would expect the enemy creatures to see you and for you to lose the benefits of attacking from hiding.
Google sage advice if you don't believe me.