comma after 'but' [conjunction]: But, it is probable that...

[sami33]

Hi

I want to understand why there is no comma after "but" in the first sentence and why it exist after it in the second sentence.

1-But I still was not sure that people were speaking English.
2-But, it is probable that it was in the theater or movie industry.

Source:Learning American English idioms Lesson 2.

Thanks

 

[entangledbank]

It's entirely optional in this position, as it often is. You can say sentences with a pause (change of tone) after 'but', or with no pause.