But I note that nobody connected to the comics has actually said that Buffy is "the most important person in Angel's life"; what Scott Allie actually said is that in his opinion she's the most important person in Angel's story.

I disagree. I think Allie was talking about the S8 narrative with respect to what Joss thinks is most important to Angel. But I don't see any other way to interpret "in the most general sense, what matters most to the character of Angel?" as meaning anything other than what (or who) is the most important thing to Angel overall, not just with respect to S8.

Of course, I also realize that's nothing more than Allie's personal opinion, and thus has no bearing on Angel's actual characterization.