Is is right if a team member moans about a 'bad performance' of another team member in retrospective? In my understanding, teams will always look at the team performance, never on a single members performance in scrum.
In the described case, a team member came back after 3 weeks of holidays and said that the 'performance' of a certain project, which is supported by just one other team member, would have been unexpectedly low. No request why this might have been the case, no constructive criticism. The scrum master didn't intervene. IMHO this is against the 'rules' of scrum - for good reasons.