tlhIngan maH. taHjaj.

The first sentence obviously means “We are Klingons.” Given that “we” are plural, it’s obvious that the Klingons that we are — are also plural.

The second sentence? Since the subject is not first person plural, we’re not saying, “May we endure.” It’s third person. Singular? Plural? Given context, I’d say plural. 

So, what third person plural noun were we just given in context? “Klingons”.

“May Klingons endure!”

Our wish is not merely that WE endure, but that all Klingons endure.

It’s stylistically appropriate to omit the second instance of the noun {tlhIngan}, though it would not be in any way inappropriate to include it. It’s just a matter of personal style. TKD tells us that repeating a noun in a situation like this is not considered wrong, yet a lot of canon examples suggest that the omission is also not in any way wrong.

So, “We are Klingons. May Klingons endure!”

It’s got nothing to do with the pronoun {‘e’} or with any attempt at *Sentence As Subject*, which is not a legal grammatical construction in Klingon. We’re just saying two different things about Klingons:

1. We are members of their race.

2. We wish them to continue/endure.

That's one possible interpretation. Here's another: it's Clipped Klingon, short for tlhIngan maH. mataHjaj!

And yet another: a noun has elided: tlhIngan maH. taHjaj ghu'vam!

Or a more specific one: tlhIngan maH. taHjaj wo'!

Or maybe this is an example of a verb whose subject is just so well understood that it's never actually stated, like when a Klingon feels water falling from the sky and says SIS. What is the subject of SIS? Nothing specific, but we understand the sentence all the same.

The point is we don't KNOW exactly what the grammar of this non-canonical sentence is, so we shouldn't go developing our understanding of grammar on it.

-- 
SuStel
http://trimboli.name