A bare README was rendered as markdown 'by convention'. libspatialite's is an autotools plain-text file whose commands carry the root prompt #, so markdown read '# sudo make install' as a heading and turned the build instructions into a dozen h2s.

Extension decides now, and anything unrecognized falls through to escaped

 with its line breaks intact — fossil's rule in
wiki_render_by_mimetype. Also recognizes README.wiki.