Comfort means something different for everyone. Although no garment should be uncomfortable. Why else would you buy it? Not counting those beautiful Louboutins.
Besides, it is different for everyone what makes you feel productive.The one is more productive in a full dressed up tailored outfit, while another works more efficient when he/she is wearing the typical comfortable clothes like knits, jeans, homewear, etc.
Moreover, the task will also determine whether you feel productive in a particular outfit.
Preparing for a presentation in a jogging outfit will be less motivating. Administrative tasks in looser clothing, on the other hand, can make an already difficult task more enjoyable.
In general, we can say that a certain minimum of dressing up is required to experience a productive feeling.