If we accept it, then who will be the one deciding, "when okrand is speaking casually, and when he's officially creating canon" ?

Precisely.

Perhaps, the need never appeared again for okrand to use {qabpaq}. So, how could someone dismiss it, as being "a one-time temporary word only" ?

A canonical word need not be a dictionary word. Klingons occasionally coin one-use words and throw them away; this practice itself is canonical. So if we accept qabpaq as canonical, there's still no evidence one way or the other whether this is a canonical throwaway term or a canonical "the way Klingons refer to Facebook" term.

Given that in our fictional Klingon world Klingons are unlikely to know or care much about Facebook — what century is Maltz living in, anyway? — what Klingon is putting the name qabpaq in a dictionary? I think that, unless Facebook itself accepts a Klingon translation of its name, any translated name will be an informal one.

The treatment of proper nouns in word lists has always been tricky. TKD itself is inconsistent. The dictionary proper lists planet names but not personal names. The KLI's word list has country names and ship names but not corporate names.

It's not really a question of what's canonical; it's a question of what needs to go in a dictionary. Is the KLI's word list a list of canonical utterances or a list of dictionary words?

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SuStel
http://trimboli.name