Even if we are never shown any other punctuation on screen, I think the wording of your statement is misleading. The marks are not actually a comma and a period. I would say that pIqaD has two punctuation marks: One for separating sentences and one for separating ideas within a sentence.

I tend to agree with this, however the ones that use the triangles end with a triangle, so the punctuation marks are clearly terminators, not separators. The cards are inconsistent as to which triangle ends sentences, and of course none of the cards have Klingon writing that is actually readable (at least, not that matches the Klingon text). It astounds me that this somehow became "real" Klingon punctuation in people's minds.

If I were given the task of inventing meanings for the two types of triangles as punctuation, I would probably do this: the up-turned triangle is an IDEA SEPARATOR. Sometimes Klingon is happy to smush two sentences together to form a single idea, as in 'uSDaj chop; chev Bite his leg off!, and these would not be separated. Conjunctions would not have their components separated. The down-turned triangle would separate dependent clauses from other clauses in an idea wherever they appeared.

For example (I hope the triangles survive the sending of this message):

juHwIj 'el HejwI' ▲ vIleghDI' ▼ qovIjwIjvaD jIjatlh 'uSDaj chop chev ▲ Haw'meH HejwI' ▼ pay' Qorwagh vegh ▲ ghaH vIHIv jIH'e' ▼ vIleghqa'chugh

But this is just my aesthetic preference, supposing I had to use triangles at all (they don't suit the usual typeface). It doesn't match what anyone else has been doing with them. (For instance, in my mind, triangles resting on their sides are stable and are more suitable for ending thoughts, where you can gather yourself for the next idea, while triangles standing on their points are unstable, meaning you have to move on to the next thing quickly.)

-- 
SuStel
http://trimboli.name