In TKD, Marc Okrand describes the use of {-‘e’} placed on a noun at the beginning of a sentence as making the noun the “topic” of the sentence.

No he doesn't. He says "Any noun in the sentence indicating something other than subject or object comes first, before the object noun. Such nouns usually end in a Type 5 noun suffix..." He gives us the example from Star Trek V, qIbDaq SuvwI''e' SoH Dun law' Hoch Dun puS. But he otherwise had given us no other indication that we can do this until he spoke to qurgh and called it marked.

Now, it's not clear to me that Okrand was specifically talking about topic nouns at the front of the sentence, or emphasized subject or objects "fronted." He mixes up the concepts of topic and focus in TKD, which Lawrence pointed out in an interview with him in HolQeD. But let's assume he does, indeed, refer to putting otherwise standalone topic nouns in front of the sentence along with locatives and ablatives and so on. Putting a topic noun there would fit right in with everything else, and there's no prohibition against doing it, but we have learned that it is marked to do so, so it should generally be avoided.

Elsewhere in TKD, it is also used on the noun in the subject position of a “to be” sentence, using a pronoun as the verb. This is not to be misinterpreted as marking that noun as the topic of the sentence. It is a separate grammatical function of the suffix {-‘e’}. {tlhIngan ghaH HoDvetlh’e’.} “That captain is a Klingon." The captain is not the topic of the sentence. It’s just the X in the grammatical construction “X is Y.” It’s a convention. Don’t try to apply outside grammatical rules to it. Just accept that this is how this is done.

As a matter of fact, it DOES mark the topic of the sentence. puqpu' chaH qama'pu''e' as for the prisoners, they are children. As for the prisoners names the topic of the sentence. The fact that it's a required grammatical form doesn't change the fact that it's a topic.

In early years of the language, SuStel pointed out that in Okrand’s examples, he rarely marked the topic with {-‘e’}, but instead used {-‘e’} for emphasis or focus. He and I argued about this, and I was stubborn at the time, but more recently have noticed, that, gee, he was right. I was wrong. My bad.

I only started pointing it out after Lawrence pointed it out to Okrand. I wasn't clear on the distinction myself.

So, the primary example Okrand gives us in TKD for {-‘e’} used as the topic of the sentence is in practice perhaps the most rare in actual use. You can recognize it because you’ll note that there is a noun at the beginning of the sentence with {-‘e’} on it that has no grammatical reason for being in the sentence without the {-‘e’}. It’s the topic, and nothing but the topic. It’s not the subject. It’s not the object. It stands apart from the {OVS} grammatical structure of the sentence, preceding it. It’s the topic because that’s all it is. It gives you a context for the rest of the sentence. You are being directed to narrow your context of ideas for the following sentence to include only the topic stated.

… or maybe SuStel called that “focus”. I get confused. Anyway...

No, focus is another word for what we're calling emphasis. This is different than topic.

The secondary example is similarly separate from all other uses. In a “to be” sentence, (dialects aside) it marks the noun used in the “S” position of “OVS” where “V” is a pronoun functioning as the English verb “to be”.

Pronoun-as-to-be sentences are not in an OVS form. They are their own special thing, just like the law'/puS sentence is its own special thing.

TKD says that in the sentences tlhIngan jIH, yaS SoH, and pa'wIjDaq jIHtaH, the pronouns are the subjects of the sentences. But if you've got a third-person noun being linked to another noun, as in puqpu' chaH qama'pu''e', the noun marked with the topic suffix is the subject.

It's easy to get confused and think of the pronoun as a verb stand-in because it has verb suffixes on it. But it's still a pronoun. This is not an OVS sentence; the Noun in <Noun Pronoun Topic'e'> is not an object. The pronoun simply "follows the noun."

-- 
SuStel
http://trimboli.name