I originally thought it was a friend zoning thing. i think it would have carried more weight if it was used on more then one person prior. Considering it was Itachi who started this I was like WTH? Not out of disgust or anything but just because it seemed like a poor attempt by Kishimoto to turn the forehead poke into something romantic instead of platonic, like if there was a flashback were young Sasuke was spying on Itachi with a girlfriend and he poked her head before kissing her then it would have had more weight emotionally. As it stands I just find it sloppy writing.