In game 4 of the World Series last night I noticed that in the 4th inning, one of the Dodger batters, the second one I think, hit the catcher in the head with his bat. Is there no penalty for this?
Manny Machado's follow-through hit the Red Sox catcher once in the series, and Xander Bogaerts did the same to the Dodgers' catcher. In either case, these were incidental contacts and a simple apology was given to the catcher. No punitive ruling was assessed, and none would be.
When it becomes an issue is if a baserunner goes to steal a base. If in this case, the batter has the same contact, the baserunner is called out due to interference.
In a more extreme case, when the umpire rules there has been malicious contact, the batter is ejected. While I have not seen a batter maliciously hit a catcher with a bat, I have seen on two occasions a batter kick the catcher before charging the mound