When I set both lines side by side I realized something I hadn't noticed before: Shade writes a poem about "life as a poem," whereas Kinbote's footnote is about "life as a footnote"  Neat. 

Kinbote's rendering is equally applicable to TOoL, although who authors the "unfinished masterpiece" remains undisclosable.

 

Man’s life as commentary to abstruse

Unfinished poem. Note for further use.

(John Shade, PF,lines 939-40)

 

                                           “…our poet suggests here that human life is but a series of footnotes  to a vast obscure unfinished masterpiece.”

(Charles Kinbote, footnote to lines 939-40)

But Shade writes of life as a commentary to a poem, not as the poem itself. Kinbote inanely explains to readers what they can read for themselves Shade wrote.

 

Anthony Stadlen