These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Alternative Character Interpretation: Did Bernie kill that woman out of sheer desperation of her dominating him and spreading her money around out of the goodness of his heart, or did he kill her in cold blood for her money and was so generous with her money to further ingratiate himself to the local population, and thus the local jury pool if and when he was caught? The fact that he didn't spend the money on himself supports this interpretation.
Also, he could have been trying to overcompensate because of his guilty conscience.
The Cast Showoff: Jack Black is allowed to show off his singing ability in several scenes in church.
Ensemble Dark Horse: That guy in the green shirt in the diner. The one who explains that Texas is really five states (then proceeds to list seven of them) and who says of the people of San Augustine, "I wouldn't let those people work on my car."
He Really Can Act: Jack Black has built most of his career on silly comedies. This is an extremely dark comedy-drama, and he does a really good job of playing that blackness for all it's worth. Then when it comes to the more serious, dramatic parts of the role, he totally owns it. Matthew McConaughey also does a really impressive job as the prosecutor.
Jerkass Has a Point: While Danny Buck is rather overzealous and eager to convict Bernie (even using some unsavory tactics), he does point out that Bernie killed someone and can't simply be exonerated because everyone likes him, especially when he confessed to his actions.
Moral Event Horizon: It appears the final straw for Bernie was when Marjorie verbally abused him for defending the African American gardener she just fired apparently on a purely racist assumption and then physically prevented Bernie from leaving by closing the property gates on him.