I can't help but think that Anne and Wentworth, in their own ways, are exhibiting a coldness and being barely civil to each other because they both feel so deeply and have not determined (each for him- or herself) how best to act toward the other.

I believe that despite appearances, his own belief, and what the ON has told us about his feelings, that Wentworth is not over Anne, much as he might wish it to be the case that "her power with him was gone forever." I believe that when he describes to his sister the woman he should wish to meet with (to marry), "A strong mind, with sweetness of manner" is precisely how he would describe Anne.

I can't and don't say that it was appropriate for him to have not extended her a normal tone and politeness, but knowing that she refused him (which none of the party knows) and believing I see that the ON is letting us in on the possible depth of his feelings for her, I can cut Wentworth some slack for being confused in her presence and not knowing how to behave more appropriately. I do notice and find it sad that none of the extended party seems to notice that his interaction with Anne is apparently not as polite as his interaction with others present, but then that seems to be Anne’s lot. Or, does the lack of mention of it mean that it is more apparent to Anne because she feels so deeply for him and otherwise not so out of the ordinary?

There are those few instances where his actions are admirable (setting up the first meeting at the cottage, the child, the gig – already discussed in other posts). And in Chapter 9, I think we get quite an interesting peak into Wentworth's possible state of mind when he walked into the cottage drawing-room and found only Anne and little Charles: "The surprise of finding himself almost alone with Anne Eliot, deprived his manners of their usual composure: he started, and could only say . . . before he walked to the window to recollect himself, and feel how he ought to behave."