The trial is absurd, as is the sentence of death, to be carried out by the people in the name of justice. Courtrooms are as much to do with theatrics as well as justice, besides Number 2 cannot allow anything to happen to Number 2, she has already said he has a future with them. A baying mob screaming for blood would have completely ruined that, if they had actually laid their hands upon the Prisoner. They might well have torn him limb from limb!
The Prisoner is not given a costume for carnival. Number 6 interprets that as being still himself. Seeing as his own suit is delivered especially for the occasion. Perhaps it's because Number 6 is still himself, or on the other hand it might be because the Prisoner is above such “bourgeois enfantine!” Either way by the end of the episode Number 6 no longer exists, he’s dead, as Number 2 puts it, “locked up in that long box…in that little room.”
Be seeing you