That's how I always understood it as well. I think the tricky bit that Squark is talking about is that it is difficult to express imperativeness when addressing oneself (or specifically in his question, "us" which has "me" implicit in it).
the fact that {ko} has "you" implicit in it always kind of bothered me as well. It still kind of does. We have attitudinals for things like "{me imperative} go to the store" with {.ai klama lo zarci} but that doesn't seem entirely right either.
It's a little disappointing to me that lojban doesn't have a more generic form for just plain {imperative} which could have {do} tacked onto it (or {mi}, {mi'o}, {da}, etc...) without the need for the clumsy {doi mi .i ko klama lo zarci}. But oh well. Maybe something to take note of for LoCCan.
I always thought "let us" (or, more commonly, "let's") was a way to
say first-person plural imperative of verbs in English. For example,
"let's go" - first-person plural imperative of the verb "to go".