Then we have the age old discussion whether Diwali is for Sikhs or not. Although most of the discussion around this topic is not worth spending time on, in my opinion, I did find an interesting article on sikhphilosophy.net of which at least one idea I wholeheartedly empathize with, and that is the first line of a shabad should not, in most circumstances be used as a refrain and sung repeatedly because it tends to change the central purpose of the shabad.
The author in the article gives us an example "ON DIWALI DAY Programmes at the Gurdwara I have often heard Raagis singing this shabad from Bhai gurdass Ji di Vaar -Diwali kee raat deeweh ballian ..." For more see http://www.sikhphilosophy.net/sikh-sikhi-sikhism/1008-diwali-ki-raat-deeweh-ballian-diwali.html
For this reason, I think it is incumbent upon us, those who sing Gurbani, and even more so for composers who have the privilege of arranging music to support Gurbani, to keep the central meaning of the shabad in mind while choosing refrains and doing the whole composition.
Popular compositions for beautiful shabads like Jo Maange Thakur, Paati Torai Maalini, Bhoolai Maarag Jineh Bataaya, and Lakh Khushian Patshaiyan use the wrong refrain -- the first line of the shabad. Incorrect repitition provides incorrect emphasis and tends to make us forget key words from the rahao which are closer to the central meaning of these shabads: Har jan raakhai, Bhooli Maalini, Simar manaa raam naam, and Ekas syon chit laye, respectively.
In the past few years this has been one of the leading guiding principles for Gurbani music composition (even ahead of nirdharit raag compositions). I have myself sung all these shabads using the wrong refrain; and now I have started singing all these shabads using refrains prescribed in the Guru Granth Sahib. And I have learned that the beauty of these shabads is far beyond than what I have been able to enjoy.
For this reason, even though the following rendition of Simar Manaa is not in Bilawal, I prefer the following composition over the next one by Bhai Harjinder Singh (Srinagar wale):