"List the file extensions that are allowed to be uploaded. Use spaces or line break between extensions. If video uploads are enabled allowed video extensions are supported automatically."
Comma. Enabled refers to video uploading being enabled, allowed refers to which specific extensions are allowed to be uploaded. Putting a / changes the meaning to make them both refer to video uploads.
Yeah, this is the kind of discussion I expect to see on the writing forums where I'm a member. Now I'm worried that a discussion of the finer points of PHP might break out on one of them.
It probably should've been a comma, but I've reworded it to be a little clearer. Plus it's actually referring to the option that now covers both video and audio uploads.