Why would it annoy Victor when his professor was complimenting him in front of Henry?
Victor is more distressed than annoyed at the compliments he receives while Henry is with him. He describes it thus:
Ever since the fatal night, the end of my labours, and the beginning of my misfortunes, I had conceived a violent antipathy even to the name of natural philosophy. When I was otherwise quite restored to health, the sight of a chemical instrument would renew all the agony of my nervous symptoms. Henry saw this, and had removed all my apparatus from my view. He had also changed my apartment; for he perceived that I had acquired a dislike for the room which had previously been my laboratory. But these cares of Clerval were made of no avail when I visited the professors. M. Waldman inflicted torture when he praised, with kindness and warmth, the astonishing progress I had made in the sciences.
Victor is nearly driven to terror by simply speaking about the theories and processes that led to his creation. So disturbed is he by what he has done that the very "sight of a chemical instrument" would torment him. For Victor, all praise he receives is a reminder of the horror he thinks he has wrought upon society. To use a cliche, it as though each kind word is a twist of a knife in an open wound. One of the sad ironies for this character is that the love of knowledge which inspired him to create life has been twisted into hate by that very creation. Of course, if Victor had attempted to understand his creature, & guided it into the conventions of human society, he wouldn't be in this position in the first place.