The deal with predicate fronting

Returning to the final concern of the previous post, let’s take a careful look at fronted predicates. Since some afternoon in the early 20-teens at the Bayfair BART station I've been saying things like

Koa ko... "It’s good that..."
Tota ko... "It’s true that..."
Te tai ko... "It’s possible that..."
Io ika ko... "Okay, let’s accept that..."

So what is actually happening here? Are we fronting the predicate because it’s focused? Or some other pragmatic reason? Is there something presentative about this, like as if we were saying

Vo te tai ko tia lu te tota! "Hey look, guys, it's possible this could be true!"

Hm. I feel like there’s something else going on. Can any of these expressions be followed by a simple predicate? Uh...I’m not sure. Maybe we first need to start out with the principle that any predicate can appear on its own, as if preceded by i. [i] koa “it’s/that’s good,” [i] mesúa “it’s sunny,” etc. So how would we append further information to that predicate?

Immediately I think of ve, in the sense “it’s good ‘how’ X”:

Koa ve ta si lai! “It’s good that she’s come back!”

But...in all other circumstances explored so far, ve is interchangeable with ko if we make the referenced clause intransitive. Is that the case here?

TIME OUT: I think I might have grasped it. The clause is actually modifying the initial predicate! If we start with “it’s good,” we could then ask “what kind of good?” And the answer here is a “her having come back” kind of good. If this is so, then there’s no problem switching to ko as I suggested above, because it ends up having just the same meaning:

Koa ko ta si lai! “It’s good that she’s come back!”

But what, semantically or pragmatically, is the difference between that and

Ko ta si lai i koa / Koa sa ko ta si lai?

The latter in particular is so straightforward: it’s a focused predicate. And it feels equivalent...but maybe that’s because I’m not thinking clearly about the pragmatics, and/or because I’ve been using sa wrong in some contexts in the past. Is “it’s good” necessarily new information?

“So Mary came back yesterday. Is that going to be a problem?”
“Actually, I think it’s good that she’s come back!”

In that dialog, koa sa feels like the right translation because in context we are genuinely focusing on new information that the speaker is contributing. So what are other possible contexts?

“But she only just came back yesterday...I’m afraid if I tell her how I feel she’ll just leave again.”
“Well, it’s good that she came back, but your feelings are still real and valid and she needs to have accountability for her impact on them.”

“Well you’re certainly cheerful this morning! What’s got you smiling so wide?”
“It’s good to have her back!”

Actually, I feel like in most contexts phrases like this are kind of neutral in focus, like the contribution of the whole proposition to the discourse is more important than the relationship of any particular constituent to the discourse stage. Maybe more relevant to the question of structure is just balance, style, flow — an aesthetic consideration? Regardless of focus, (A) the critical piece of information being communicated is the predicate and as such it’s weird to bury it under a whole clause, and (B) if the subject is the dependent clause, an issue of parsing arises where we have to figure out where we’ve rejoined the matrix clause again, potentially pretty far down the line if the dependent clause is complex. It’s just a lot easier to understand with that bit of information out in front.

Two main points:

1. Te tai ko-type clauses are motivated by existing Koa principles and clearly grammatical
2. Their use is reasonable both for pragmatics and style and not just an IE calque.

However note: it’s also become apparent in the course of writing this that in the past I’ve unintentionally used sa as a kind of presentative particle which I think is not motivated by pragmatics. I need to be careful and remember that bare-stem predicates carry meaning on their own!