Śrīpāda Śaṅkarācārya has unceremoniously obscured the Kṛṣṇa consciousness described in the puruṣa Vedānta-sūtra by manufacturing an indirect interpretation and abandoning the direct interpretation. Unless we take all the statements of the Vedānta-sūtra as self-evident, there is no point in studying the Vedānta-sūtra. Interpreting the verses of the Vedānta-sūtra according to one's own whim is the greatest disservice to the self-evident Vedas.
As far as the oṁkāra (praṇava) is concerned, it is considered to be the sound incarnation of the Supreme Personality of Godhead. As such, oṁkāra is eternal, unlimited, transcendental, supreme and indestructible. He (oṁkāra) is the beginning, middle and end, and He is beginningless as well. When one understands oṁkāra as such, he becomes immortal. One should thus know oṁkāra as a representation of the Supreme situated in everyone's heart. One who understands oṁkāra and Viṣṇu as being one and the same and all-pervading never laments in the material world, nor does he remain a śūdra.
Although He (oṁkāra) has no material form, He is unlimitedly expanded and has unlimited form. By understanding oṁkāra one can become free from the duality of the material world and attain absolute knowledge. Therefore oṁkāra is the most auspicious representation of the Supreme Lord. Such is the description given by the Māṇḍūkya Upaniṣad. One should not foolishly interpret an Upaniṣadic description and say that it is because the Supreme Personality of Godhead cannot appear Himself in this material world in His own form that He sends His sound representation (oṁkāra) instead. Due to such a false interpretation, oṁkāra has come to be considered something material, and consequently oṁkāra is misunderstood and eulogized as being simply an exhibition or symbol of the Lord. Actually oṁkāra is as good as any other incarnation of the Supreme Lord.