1. Is there anything wrong in using *'op* with inherently plural nouns, for example: *'op ngop*? The whole construction would remain grammatically singular, right?
I don't think we have a definitive answer to this question.
Personally, I have no problem with 'op ngop meaning
exactly what you say. I believe we do know that you can use
numbers with inherently plural nouns, so I see no reason you can't
use number-like nouns in the same way.
2. If I want to say *She hasn't sold it*, I can say *ngevpu'be'*. What would *ngevta'be'* mean? That she set out to sell it, but she didn't accomplished it? Has *-ta'be'* always the meaning of failing? Or can we also use it just to negate that an action took place?
-be' seems to have a variable scope. Sometimes it applies directly to the element it's attached to; sometimes it applies to everything that comes before it. ngevpu'be' and ngevta'be' probably mean "not ngevpu'" and "not ngevta'."
I generally try not to think of suffix combinations as single
units. It might not be useful to think of -pu'be' and -ta'be'
as having distinct meanings from -pu' and -ta',
because the -be' may not apply only to -pu' and -ta'.
If I were to give a literal interpretation to -pu'be'
and -ta'be', it would be "not perfective," which would
seem to mean exactly the same thing as not including the
perfective suffix at all, and so not be a useful combination.
3. To someone whose decision in a certain situation can have important consequences, I can say *Be responsible!*. That would be, I think, *yIngoy''eghmoH*. But if, speaking to an inmature person, I say *Get responsible!* or *Become responsible!*, would it be *yIngoy''eghchoHmoH* or just *yIngoy'choH*? (I know there is the verb *moj*, but I would like to know how the imperative of state / quality verbs works).
I'd go with yIngoy''eghchoHmoH, but canon is inconsistent
with the -'eghmoH rule when it comes to including -choH.
If you use the yIngoy'choH, it will likely be accepted by
whoever reads or hears it. What Klingons would think of it, I
don't know.
-- SuStel http://trimboli.name