Theory about telepaths
Telepaths inflict either positive or negative effects on people they continuously read from. We see Loid, Melinda, and the Grandpa Neighbor think something along the lines of "that sinking feeling is back". The "sinking feeling" is the residue of mind-reading. Which is how >!the grandpa next door realized Anya was a telepath since he was shown to have the sinking feeling and then immediately realized she was 007!<.
Anya is a positive telepath. Both in her attitude and the affect she had on people. She positively influences Loid and Damian, breaking down their walls with cuteness and unknown help from her powers. That's why people are happier when they interact with her.
Donovan, however, is a negative telepath. His mood and the way people act around him are both negative. How his family shuts down when they are around him. Negative telepaths also chip away at the sanity of the people they read from. Hence why Melinda and Demetrius act the way they do. Damian hasn't interacted with his father enough for it to affect him as much as the other two, which is why Anya's positive energy seeps into him easier.