That is definitely a tape joint with the updated pics. It looked like to me before the tape joint was 2 inches above the brown and it wasn't painted to corner( see first response)
Xeq is you look in the left corner in the first picture, that is water damage, down both ceiling and wall seams.
If this is a exterior wall you either have gutters needing cleaned, or no drip edge or a roof leak someplace higher and water is penetrating into your home. If it is a more interior wall, you have a leak somewhere on roof.
Do you own this home? Post a picture next of the roof above that area please( from the ground is fine )
Noodle-Sorry no experience with them.