My wild guess at why the exceptional {‘e’ neHbe’ vavoy} exists is that the expression is already exceptional, since she’s already using {‘e’} to represent something someone ELSE said.

I agree that that's the most likely explanation. You have to hang the neH on something.

Meanwhile, my understanding was that {ja’} could take nouns (in particular people or languages} as objects, but I didn’t remember canon showing it taking quotations as objects.

No, it doesn't take quotations as objects, I said it references quotations — that is, it can be used as a "verb of speaking." This is described in the "sentence as object" section of TKD, but quotations are not described as objects.

The canon shows us that it can take the addressee as its object, e.g.:

loDnI'Daj vavDaj je ja' qeylIS
    nIteb peghoS
    HatlhDaq peleng

Kahless tells his brother and father
    to go their separate ways,
    And travel the lands. (paq'batlh)

The canon also shows us that it can take a noun describing the matter spoken about, e.g.:

wIj jup
    SengmeywIj vIja'laHbe'
    jIHvaD ratlh pagh

Dear old friend,
    I cannot speak of my tragedies,
    There is nothing left for me.

As a side-note, notice that the first example includes both an addressee object and a quotation. And notice that Okrand uses a direct quotation to translate non-quotation description of what was said.

I have deliberately chosen these examples as completely unambiguous: no wonkiness with prefix tricks or reflexive objects.

I believe these sentences illustrate how the Klingon syntactic role of "object" can be played by a word with the semantic role of "direct object" or a word with the semantic role of "indirect object" (or, very crudely and not-comprehensively stated, "patient" and "recipient").

I know it can be used as the speech verb in the sentence pair with a quotation as one sentence and the speech-verb-sentence as the other member of the pair, but grammatically, they are independent. One is not the object of the other. That’s why the order of the two sentences is completely unimportant.

DuneH HoD. qaja’ta’.

qaja’ta’. DuneH HoD.

It means, “I told you, ’The captain wants you,’” regardless of what order the sentences are presented. The quotation isn’t the object of {ja’}.

And a better translation, one which fits in with Okrand's own usage, would be:

DuneH HoD qaja'ta'
qaja'ta' DuneH HoD
I told you that the captain wanted you.

We would more naturally do that without a quotation. Klingon does it with quotations.

I won’t be remarkably surprised if you present canon contrary to this because I know how careful you are and I respect your encyclopedic memory of canon. I’ll just be disappointed in Okrand for yet more problematic canon.

I don't know of any canon of 'e' ja', if that's what you mean. This is what I've been trying to say. Canon shows us the object can be the addressee (as indirect object) or a description of the matter spoken of (as direct object), but the actual content of what is told must be a quotation.

Theoretically, you should be able to formally say things like

HoDvaD nuHmey Dotlh ja'pu' ya, Qapbe' nISwI' cha'.
The tactical officer told the captain regarding the weapon status that disruptor number two wasn't working.

-- 
SuStel
http://trimboli.name