SuStel:

jIQam; jIba' 'e' qa'
I stand instead of sitting.
This is literally I stand; it replaces that I sit. You cannot say jIQam; jIba' qa', because the object of qa' replace cannot directly be a sentence. You need the pronoun to stand in for it.

Maybe I'm missing something here, but what is actually the subject of *qa'* in this sentence? I would say that is the first sentence (*jIQam*), something like *That I stand replaces that I sit*. But since sentences as subjects aren't possible in Klingon, I cannot understand this structure properly.

This is one of those cases of Okrand giving us what appears to be a fixed expression that doesn't follow the rules. I'm not sure it makes sense to ask what the subject of qa' is here.

-- 
SuStel
http://trimboli.name