[Advaita-l] Pre-Shankara Upanishadic interpretation ?

[V Subrahmanian]

Namaste.

While commenting on the MundakopaniShad mantra 1.2.11 -

तपःश्रद्धे ये ह्युपवसन्त्यरण्ये
शान्ता विद्वांसो भैक्षचर्यां चरन्तः ।
सूर्यद्वारेण ते विरजाः प्रयान्ति
यत्रामृतः स पुरुषो ह्यव्ययात्मा ॥

[ Those who live in the forest, while begging for alms - those who resort to
the duties of their respective stages of life as well as to meditation - and
the learned (householders) who have their senses under control -  they after
becoming freed from dirt, go by the path of the sun to where lives that
PuruSha, immortal and undecaying by nature.]

Shankaracharya, after explaining the mantra, interrupts with a question:
ननु एतं मोक्षमिच्छन्ति केचित् [Is not this state considered to be liberation
by some?]

and proceeds answering in the negative and gives reasons thereof by taking
up the mantra and clarifying by pointing out the positioning of the mantra
and the meaning of a particular word there too.

The question and answer give one an impression that Shankara is referring to
someone's (s') केचित् interpretation of this mantra and if such is the case,
could this be seen as a case of the presence of a commentary or something of
that sort of the Mundakopanishad during His time?

I would like to hear about other similar cases in the Bhashyam of this or
other Upanishads.  There are cases where Shankara gives alternative meanings
to the same word/mantra with 'atha vaa'.  This is a different case.

The following article is worth reading:

http://www.advaita-vedanta.org/avhp/pre-sankara.html

Regards,
subrahmanian.v