A member who has exhausted their right to debate can still debate the merits of the main question during the debate on which motion?

The ability for a member to debate the merits of a main question, even after they have exhausted their right to debate, applies specifically in situations where a motion to postpone indefinitely has been made. When this particular motion is introduced, the member can still engage in discussion regarding the main question because they are effectively debating whether the assembly should postpone the question rather than the main question itself.

In contrast, when discussing other motions such as "postpone for a definite time," "close debate," or "reconsider," the context differs. Motions to postpone for a definite time do not lend themselves to debating the primary issue since they focus solely on rescheduling the consideration of the matter. A motion to close debate restricts discussion altogether, rendering any debate on the main question impossible. The motion to reconsider primarily deals with revisiting a previously made decision rather than engaging in the ongoing debate related to the main question.

Thus, the motion to postpone indefinitely allows members, even those who have exhausted their general speaking rights on the main question, to argue for or against the idea of setting the question aside permanently, enabling them to continue participating in the deliberative process.