text: I think you are right, no matter how interesting their conversation may have been, your friend should have had the courtesy to stop for a moment to introduce you as you were together since the beginning, however as a demonstration of education it would be acceptable that you waited for the perfect moment during their conversation to introduce yourself with a positive comment emphasizing the good aspect of making new friends or simply encouraging their conversation.  \n\nHaving manners often implies having empathy with others.