terminate return value logic is very unclear. It is actually about stacking messages on the initial message, but the description is too cryptic about this.

(Also, the description is tl;dr and very obtuse in general, it should be rewritten to be more concise.)

The order of ForwardMessages within the Vec is irrelevant. It is only important that the Vec contain all message forwarding events that are immediately triggered by msg.

This is only done for random tests; fixed tests expect a specific order.

Description contains key errors:

0 < sender < n identifies the sending player with successor(x) = x + 1 % n and predecessor(x) = successor⁻¹(x) describing the cyclical order of the players.

It should be 0 <= sender < n and successor(x) = (x + 1) % n