I came across this situation of someone who is invited as a guest for the sprint planning meeting taking an higher interest in the architecture of the product, creating a conflict of interest between the development team and the guest. Yes, someone dominating a meeting due to his expert power can be a violation of scrum. If this is due to the huge technical deficit between him and the rest of the team, then it is good for the product in the longer run. Now, here is the question of process vs product. We are following a certain set of processes to build a great product, and we must be open to all ideas and suggestions, if it is adding value to the product. This situation, if not managed properly can spoil the team morale and the product. Scrum master is trying to sort it out by only talking to the development team by asking them to prevent the expert from dominating. Personally I feel that it would be better, if the scrum master could talk to the expert one to one and sort it out. Leveraging expertise without stifling teaming, innovation and knowledge sharing is a must for better teaming and a great product.