SuStel:

I have no problem at all with allowing
qatlh and chay', which work just like adverbials

I'm afraid I can't understand this. Why do the {qatlh} and {chay'}
work like adverbials ? How can a question word work like an adverb ?

In general linguistic terminology, an adverbial is a word or phrase that modifies a verb is done. chay' asks how a verb is done. Describing how a verb is done is adverbial. qatlh is a little less obvious, but when you describe the reason something is done, that's also modifying the verb.

Since chay' and qatlh relate to adverbial concepts in general linguistic terms, it's not a stretch to suppose they resemble the class of Klingon words that Federation linguists call adverbials, at least in their placement.

Remember that to Klingon linguists, these are all just chuvmey. They don't make these deep distinctions. And non-OVS elements tend to just get thrown in the soup of words at the front anyway.

I'm not saying this is absolutely true, just that I wouldn't find it unreasonable to place chay' or qatlh in a sentence according to the same logic that you would place any adverbial.

Even if the {chay'} and {qatlh} can indeed follow a noun marked with {-'e'}..

1. Is there a rule prohibiting their being placed before it? Is there
a rule which forbids us writing: {qatlh 'avwI''e' Dachotpu'?}?

No.

The only issue which I can think of, is that when we write {'avwI''e
qatlh Dachotpu'?} the translation goes "as for the guard, why did you
murder him?". But if we write {qatlh 'avwI''e' Dachotpu'?} then the
meaning becomes "why did you murder *the guard*?". i.e. instead of the
"as for.." we have an emphasis.

The rule from the TKD addendum lets you "front" objects marked with -'e', put them before adverbials. They apparently remain objects, at least as far as the wording of TKD goes. That means they still represent focus, not topic. However, I bet it's the similarity between topic and focus that lets one do this fronting in the first place.

Basically, 'avwI''e' qatlh Dachotpu' could be interpreted either way.

This is an area of grammar we don't have clear information on, so you're not going to get a satisfying answer.

2. What happens when the question word is {ghorgh} or {nuqDaq}?

ghorgh and nuqDaq also play adverbial-like roles. In wa'leS mamej We leave tomorrow, the wa'leS is a noun, but it is playing an adverbial role in the general linguistic sense. It modifies the verb. It is not what Federation linguists classify as a Klingon adverbial, but the role it plays IS adverbial.

-- 
SuStel
http://trimboli.name