It would help to allow filtering of content when inlining pages. For example, given some way to filter out the display of inlines within other inlines, a blog post could allow easy inline commenting by putting an inline directive with post form at the bottom of the post.
That's trying to do the same thing as the todo item discussion page as blog. Difference is that you're suggesting displaying the comments in the blog post that they comment on, instead of on the separate disucssion page. Which leads to the problem of those comments showing up inlined into the blog.
I know there are benefits to having the comments on the same page and not a separate discussion page, but it does add compliciations and ikiwiki already has discussion pages, so I'm more likely to go the route described in discussion page as blog. --Joey