Aha, now I remember that story.

I reacted to it as a subversion of the woman-as-obstacle trope, not as just another repetition of it. As you said, Akira's wife was more than an object; the author attempted to draw and understandable, human character. In the end, I thought that she was more sympathetic than Akira.

In slash it's almost a foregone conclusion that the male-female pairing will break up somehow. I suppose that for me that how it happened was more important than that it happened at all, in deciding whether or not I thought the story was sexist. When I think of woman-as-obstacle stories, I think of stories where the women are just obstacles and nothing else--they exist only to hold the male character back. I didn't even put Inertia into the same category because I don't think you can say that's true of the female OC.

Well, now I at least understand what some people are thinking.