Dear Antediluvian,
Salamun Alaikum.
My humble efforts to study God's scriptures may have left me with a more nuanced position as compared to others who you may be implying by citing the term 'Quran-aloners'.
Albeit this is a general observation and not a criticism against you personally, I feel such an epithet against anyone who attempts to uphold the veracity and judgment of God's scriptures is not only crude, but equally crass.
When understanding the traditions of an ancient people that have sought best practice (their Sunna) in light of the Quran, we need to exercise 'hikmah'. Not reject it, but ardently understand it. After all, the Quran references itself as huda (2:2 - guidance), a furqan (25:1 - criterion of right and wrong) and a 'meezan' (42:17 - a balance, weighing tool). This I have comprehensively mentioned in other articles which is a sentiment I trust you will concur with.
As far as your pointed question is concerned, and in particular reference to a certain 'Sunna' (practice) being 'binding', I find this unsupportable from the Quran. The Quran does not in my view make any practice of a people 'binding'. It only makes 'binding' its own instructions which as far as the Prophet and his contemporaries were concerned, took into account the immediate audience, their societal norms, practices and beliefs.
If the Prophet was alive today, it can be convincingly argued that any revelation to him would have first taken into account his immediate societal settings and dealt with any immediate difficulties with respect to his ministry in his own context.
With respect, and as one being well aware of Javed Ghamidi's position, it is to be proven that the Quran 'authorises' as religious decree, a certain Sunna of a people. I contest that there is no such authorisation in the Quran. Whereas brother Ghamidi may be comfortable in 'binding' certain practices and what 'may' and 'may not' constitute Sunna, these are with respect, his own assertions. Others may find this a subjective approach and not wholly cogent in light of the Quran.
However, I do agree with brother Javed who if I understand correctly, does separate 'religious' practices (Sunna) with those of the Prophet's 'personal practices'. This is in my humble view and in light of the Quran, absolutely correct.
Indeed certain religious practices such as prayer find immediate sanction in the Quran. Now a Sunna supporting this religious instruction may present a guide as to how the earliest Muslims thought best to practice this religious instruction of prayer, such as prayer in Arabic, where to put one's hands etc, but the Quran did not seek to define such a specific ritual.
The details of 'form' and 'utterance' (content) are absent in the Quran. This does not sanction a 'sunna' but allows for 'fluidity'. So whether one binds their hands on their navel, chest or neither, is not instructive.
By binding a prayer, for example in 'Arabic' who has no understanding of the Arabic language is in contradiction of so many verses, not least of the implied 'instruction' not to approach prayer - hatta ta 'lamu ma taqulun (until you know what you are saying) 4:43. Albeit it can be argued that 'sukara' can capture any state in which a mind is not in mental equilibrium, the implied instruction that one must know what they are saying is present.
Here it can be argued that the 'hikma' behind such silence as not to prescribe 'content' or in a particular language allowed for the recognition of God's complete creation which He created with varying languages (30:22).
Sunna needs to be understood in light of the Quran. Nothing is binding in my view apart from the direct instructions in the Quran. However, 'religious sunna' should also not be ignored and fully appreciated in so much as to at least understand how the earliest communities best understood the Quran's commandments and sought to implement them.
The noble prophet applied an inspired revelation to him which carried many timeless edicts to his immediate time specific context. We need to understand this with 'hikmah' (wisdom). This point I humbly feel, is sometimes overlooked by some Muslim theologians.
The Quran remains final judge for believers (6:114).
I hope this helps.
Joseph.