There is no formatting, because formatting would require non-text characters. Page width is a form of formatting, so no page width can be specified. Therefore, each line must end with a carriage return , because there is no maximum width at which to break the line when reading the file. Page length is also a form of formatting. There are no pages in plain-text.
Indentation is a form of formatting.
Indentation must be accomplished with spaces. There are a number of things which we absolutely require in a plain text version of a play. These are the things which are either hardest, or impossible, for us to fix using our text editors. If we receive a plain text version of a play that does not fit these requriements, we will not accept it. One, they make life easier on us, which will assuredly expedite the listing of your play.