It is also grammatically correct and possible, would you care to and would the other person to whom you are speaking, being that they have to comprehend what you want to say, be able to follow what you are saying, in English, and I am sure many other languages, given that, while English is a somewhat odd language, it is certainly not wholly unique in any grammatical aspect, to nest clauses.
But that doesn't mean that sentence is easy to follow in writing, and even less so if spoken.
Of course, that says nothing grammatically about nested san...sìk. Just that if it were used (grammatically or not) it could get confusing.
But here's something else... We have an example of "peng" being used for indirect-like speech. "Ayolo'ru alahe peng ziva'u" and "For peng syeraw toruk makto". While that part of the movie dialog was heavily edited to shorten the Na'vi and another part did lose the "san...sìk", the impression I got from Frommer was the part with "peng" did not have the san...sìk.
So it's possible that it could just be *Oe poru poleng kawkrr rä'ä plltxe san ke fkeytok lì'fya leNa'vi. However, that idea leaves a bit of an uncomfortable semantic overlap between peng and plltxe, with different grammatical forms of each. Consider...
He said to me, "Leave!" - Po oeru poltxe san hivum!
He told me to leave. - *Po oeru poleng hivum.
One of the many outstanding questions.