What is the difference in meaning when a comma is present before 'including,' or 'such as,' and when it is not?

New Member06
With the comma, the following phrase becomes parenthetical, that is it is unrestrictive, added information.
Veteran Member114,970
SystemAdministrator: A system administrator takes care of the inner workings of the entire system. These users have the ability to promote, ban and modify other users.Teachers: Users in this role are certified teachers. This may include DELTA, CELTA, TESOL, TEFL qualified professionals. Email a scan of your qualification to an admin, if you wish to be considered.
It depends on whether or not the added material is essential or nonessential. Is it necessary to the meaning of the sentence...or just thrown in as additional information? If it's essential, no comma. If it's nonessential, comma.