clw_uk wrote:Can ones practice be frutiful (and lead to nibbana) without referring to the commentaries?
It depends on the "one" who's practice we are talking about. For some it will be necessary and for others it won't. What you are really asking is if it is necessary for you. The answer is: How should I know? I don't know you.
But really, I see no difference between this question and asking if you need to read the Digha Nikaya and the Majjhima Nikaya or if only one nikaya is enough. My answer is: why look for shortcuts? If you find the time and inclination to read more then read more. If you feel your practice is progressing fine as it is then don't read more. It's up to you to monitor your own practice.