Mine is just over 1KLOC :-) But it includes both a RSS and a JSON feed, support for Twitter card / Facebook sharing, a calendar view, and a tag cloud. Live demo: https://plurrrr.com/
The choice of using one markdown document to render all the pages is really interesting to me. Do you just edit the document in your terminal? Trying to imagine the usability of that, I guess if I was quick at jumping from one "page" to another it might be faster than opening and closing files.
I use Emacs to edit the page in Markdown mode with some additional font locking I wrote. It looks very similar to the actual blog.
Currently the input file is 1.4MB (828 blog entries) which Emacs can handle without any problems. Searching works very fast. I keep the file open and writing a new entry is just adding stuff to the top of the file.