Good catch, Tom - that setting is a little low. I just bumped it to 15 globally.
I took a look, and didn't see an individual setting. My guess is, most site owners wouldn't want this setting to be bypassed, for a couple reasons.
First - performance. If users were allowed to individually set a huge number for displayed posts, the database query to fill the page could easily overwhelm the server.
Second - many site owners, have revenue concerns. If ads are displayed on each page, increasing the number of posts per page reduces the number of ads displayed - more pages viewed, more income. This doesn't apply here, as Ranger's sponsorship of the site is keeping things ad-free, I just mentioned this as a possible reason for the limitation.
The number could certainly be higher than 15, if folks wish it to be so. However, that's what it is set to at the "other site", and seems to work well over there.
Heh...the first "other site" reference. 😀