What is the significance/what techniques are used in the quote by Portia, 'I may neither choose who I would, nor refuse who I dislike.'

Repetition is used in the above passage. It is significant because it accentuates the fact that Portia is still controlled by her father's will..... even after his death. She is not independent, she cannot make her own choices. In regard to her husband, her father's choice will still trump any independent choice she may wish to make on her own.