Commanche's glasses disappear during his encounter with Eddie Zero.
When Commanche first meets Eddie Zero. He pees on his boots. Eddie Zero pulls out his pistol and pulls the hammer back prior to pointing it at Commanche's head.
Commanche then takes the gun away and re-cocks the gun as he points it at Eddie Zero.
Assuming the person that was with The Deuce at the Cherokee Kisum killing on July 4th, 1975 was Billy Wings, due to the accent ("Deuce, She's Gott'a Burn"). Billy Wings would have been at least 50 years old in 2008 (like Michael Madsen). Billy Wings character would have looked and acted much older than Vinnie Jones, who was born in 1965.
When The Gent sets his pistol down on Dani's bar, it is facing her. Moments later as he takes off his gloves, it is facing him.
The rear brake on Pistolero's bike changes from an early style drum brake in the first scenes to a later banana caliper style disc brake in the peyote scene. Then it changes back to a drum brake in the final scene.
1% MC biker gangs of the 1950s, 60s and 70s were not integrated and were segregated to white males only. Goody Two Shoes (Michael Beach), would not have been a black man. Most 1% MC biker gangs follow these same rules to this day.
Pistolero's rubber knife bends when he wipes it on Billy Wings's vest.
The word/name Deuce as shown is misspelled as "Duece".
When The Gent is talking to Comanche while at St Louis funeral, the shadow of a boom mic is visible on the ground behind them.