Rilla is the only one of the Anne books I still go back to reread on the regular. Mostly because of Susan, I think; she's so much fun and so reassuring and has so many wonderful bon mots (usually ending with "and that you may tie to," which it took me years and years to realize was a maritime term). And it's interesting that, for all the short shrift Montgomery gives to her pacifist character, as you say the book is not exactly hawkish in its actual treatment of war (the state Jem comes home in as well as Walter's death, among other things).
I did not know about _The Blythes Are Quoted_ at all, thank you for the writeup. (I think actually writing a full version of Walter's war poem was always doomed to failure, given how famous she has it become.) I picked up a copy of Montgomery's published diaries somewhere at one point, from her teens through her marriage, I think, and found it a riveting depiction of a slow spiral into clinical depression (and decided I was never ever going to read it again). No wonder her last work is so unhappy :(