last digit(s)...
1 and Yi Sang says "Ideal"
2 and Faust talks about Faust in Third Person
3 and Don acts retarded or says an english word wrong.
4 and Ryoshu says an Acronym or mentions "art"
5 and Meursault doesn't do anything unless ordered
6 and Hong Lu offhandedly reminds people of his rich Wing CEO family
7 and Heathcliff acts recklessly (pre Canto 6) or mopes about his dead girlfriend (post Canto 6)
8 and Ishmael snarks at someone
9 and Rodya eats a Hamburger
10 and Dante needs something explained due to Amnesia
11 and Sinclair wants to chicken out of something
12 and Outis acts like she's still in the military
13 and Gregor doesn't remember something's or someone's name.