Yet another two sentences

[wm.annis]

One question though: In Tsun oe ngahu pivängkxo a fì'u oeru prrte' lu, you say that fi`u is nothing more than a dummy noun for the a to connect to.

Exactly.

The very next word is oeru, also a noun. Is it because the entire clause up to oeru is essentially the accusative argument to the verb lu that you need the fi`u as a dummy noun?

Actually, in this example everything up to a fì'u is the subject, with lu the verb and prrte' the adjective complement.  "This I'm-able-to-chat-with-you thing is pleasant."  The oeru is a dative, what old-fashioned Greek and Latin grammars might call a "dative of interest," indicating the individual for whom the statement applies (i.e., "to me").

[`Eylan Ayfalulukanä]

Tsun oe ngahu pivängkxo a fì'u oeru prrte' lu

Actually, in this example everything up to a fì'u is the subject, with lu the verb and prrte' the adjective complement.  "This I'm-able-to-chat-with-you thing is pleasant."  The oeru is a dative, what old-fashioned Greek and Latin grammars might call a "dative of interest," indicating the individual for whom the statement applies (i.e., "to me").

Why doesn't prrte` become aprrte` in this sentence, if prrte` is an adjective?

I am assuming then by this example that other noun forms can follow lu (like the dative oeru in this case), but not a direct object?

[kewnya txamew'itan]

Adjectives only take -a- when they're being used attributively (that is, when they describe a noun directly), if they're used with a copula verb like lu or lam (he is tall, she seems angry) then it doesn't take -a-.

And most noun forms can follow lu, the dative can, nouns with adpositions can etc. but lu is intransitive so it can't take an accusative object.