Comma after introductory phrases
Agile software development often encourages people to write up user stories using a given formula. The formula is: "As a User I want to something so that reason for something". Some example of this formula put a comma after "As a User", some do not.
So which is correct and why:
"As a Visitor I want to view your products so that I can buy something"
"As a Visitor, I want to view your products so that I can buy something"