Due to a question brought to the TrOs, the following update has been added to the main Trials Rules post:
During this event, all matches must be played using the same account you used when registering for the event.
This update was not without serious deliberation and was made (as much as possible) without regard to the current situation and/or involved players, but from the perspective of the integrity of the event as a whole. This rule is already present in the other major PvP events War and for weekly tournaments, and that feels like sufficient precedent to make this change, even at this stage of the event.
To the best of my knowledge, no other player has used another player's account thus far in the 8th Trials, and had this been expressly legal, it may have been to their advantage to do so. I believe they have not done so because it is in the spirit of the event and generally understood etiquette to use one's own account for all sanctioned events. That it was brought into question does not reflect poorly, in my mind, of those who might want to avoid it, as it was not expressly illegal before now, and they were within their right to do what they felt would give them the best chance to win within the rules. But I feel it necessary and important to make this an official rule, and as such, it will not be allowed this Trials.