Didn't Alexandra say that he (Dmitri) behaved like who ever he was with for the moment? That might be something to consider too. I wish I could remember where I read this. I know Felix admitted that he charmed people often. He writes afterward in "Lost Splendor" that he knows saying so sounds vain.
I think that was from the book 'A lifelong passion" Felix did mention have a strong influence on his (dmirti)character. I also find it a little strange how he describes Dimitri, as almost like how he would describe himself.