I think it's different because the object of {SIv} is something the subject is wondering about (and thus may or may not be true), whereas the object of {Sov} is something that the subject knows (or doesn't know, in the case of {Sovbe'}) and should be a fact.

But in the case of chabwIj nIHpu' Mike 'e' vISovbe' you're supposing that chabwIj nIHpu' Mike is a statement of fact, while with tlhIngan Hol Dajatlh 'e' vISIv you're supposing that tlhIngan Hol Dajatlh is a hypothetical.

I put it to you that Klingon doesn't actually distinguish whether the first sentence of a sentence-as-object is indicative or subjunctive. English makes the distinction with the if or whether or that, but Klingon does no such thing. So if you're someone who doesn't know whether Mike stole your pie, you have clear context to say chabwIj nIHpu' Mike 'e' vISovbe', and it'll be interpreted as a subjunctive clause, meaning I don't know whether Mike stole my pie.

We see this sort of thing in canon a lot. For instance, when Klaa says «qIrq vIjeylaHchugh,» Vixis responds «qIbDaq SuvwI''e' SoH Duj law' Hoch Dun puS.» Vixis's statement is subjunctive in context, but it's not marked as subjunctive in any way. She's not saying Klaa is the greatest warrior in the galaxy; she's saying he would be the greatest warrior in the galaxy if he could defeat Kirk.

So I see no problem with saying chabwIj nIHpu' Mike 'e' vISovbe'. I'm taking the statement chabwIj nIHpu' Mike, never mind whether it's a fact or not, and saying that I do not know it. If the context were "Hey, did you hear that Mike stole your pie?" it would be interpreted as "No, I didn't know that Mike stole my pie." If the context were "Hey, has Mike stolen your pie?" it would be interpreted as "I don't know whether Mike stole my pie."

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SuStel
http://trimboli.name