こう言った vs そう言った

[Lomaster]

So far i've seen both 彼女がそう言った。「direct speech quotation] and 彼がこう言った。「direct speech quotation」 Are they interchangeable in such situations when direct speech is quoted?
Also, is it always (。) preceding direct speech, or can i use (、) or nothing at all?

 

[Toritoribe]

So far i've seen both 彼女がそう言った。「direct speech quotation] and 彼がこう言った。「direct speech quotation」 Are they interchangeable in such situations when direct speech is quoted?

そう言った can't be used when the direct quotation follows it. こう言った can be used both for the ones preceding or following it.

〇「こんにちは」彼女はそう言った。
×彼女はそう言った。「こんにちは」
〇「こんにちは」彼女はこう言った。
〇彼女はこう言った。「こんにちは」

Also, is it always (。) preceding direct speech, or can i use (、) or nothing at all?

A period or comma is needed. If nothing is there, it could be misinterpreted that 言った modifies the quotation (e.g. そう言った「こんにちは」は、彼に届かなかった。).

 

[Lomaster]

Thank you for the detailed answer, Toritoribe. Glad i can use a comma instead of a period.