There is a famous fried chicken recipe of Google chef Charlie Ayers . This recipe calls for marinating chicken in the fridge for 5 days. However Nestle, and USDA say that marinated chicken should not be kept in the fridge for more than 2 days. So which is right?
I would suggest going with the advice of the USDA over Nestle corporation. That said, the USDA site does not state that longer than 2 days is unsafe, rather that marinades, which tend to be acidic, begin to break down the protein after this point. That is a texture and preference issue rather than a safety issue. The recipe you link contains buttermilk (also acidic). I suspect that this will impact the texture of the final product IF it were held for 5 days. However, the recipe does NOT say to marinate for 5 days, but that you can hold it for UP TO 5 days.
Marinades are a surface treatment. You don't get added benefit beyond a few hours. The marinade does contain quite a bit of salt, so there may be some brining happening. Again, not much added benefit after a few hours or a day.
In the end, I would be personally more concerned with texture. Over night is plenty...maybe two days....yes it will be safe at day 5, but you might not like the texture as much.