This looks like a noun, but it isn’t. In the third sentence of the LCC2 Relay Text, concerning a talking rock, it occurs between a relative pronoun ien and the relational la. The only things that can occur in this position are conjunctions, clause-level modifiers, and peripheral phrases headed by some sort of prepositional particle. jalā functions as a clause-level modifier and indicates complete agreement with the statement one is responding to.
temle ke makīþa matēnnā ien jalā la liēn makīþa matēnnā;
The talking rock said to me, “Yes, I am a talking rock.”
Notice that the talking rock does not use the reduced first person pronoun.