Even when power relations are not the primary challenge with an authorship decision, the complexity of academic relationships may still influence and complicate authorship decision-making.
For example, there could be 2 or more contributors who have done very similar amounts and types of work. How should they decide on authorship position? In our context, we have seen long-term collaborators who find themselves in this situation. A common strategy is to take turns as first and second author, or first and last author. Over the course of a career, this trading of positions between equal collaborators can satisfy standards of fairness. Some journals will also allow "co-first author" submissions; whether or not this is recognized widely as a legitimate practice likely varies across people and contexts.
In the case of supervisor-student relationships, a common practice in our context is to have the student take the first author position and lead all aspects of the study and the writing of the manuscript with close guidance from their supervisor, who takes on the last author position. A careful consideration in these cases is how much a supervisor should edit the work. Whose voice should be heard? We do not have a clear-cut answer to this question. The grey area of these decisions emphasizes why ethical authorship practice requires a critically reflective approach.