I am super confused, I'll admit, on this whole concept of Flowey not being able to feel anything. The mere fact that he's just sitting there, talking to Frisk, and the way he's telling them to give up, gives the impression that he's feeling some sort of regret toward his past actions. Plus, his statement that he doesn't deserve to be saved implies that he is a little bit angry at himself as well. How would that work, if he can't feel anything?