Update.
My awesome sister-in-law sent me this, which allows me to rename “/?page_id=1386” as “/blog”:
hey,
at your root folder, create a file called .htaccess
in it, put this:
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /blog/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /?page_id=1386 [L]
</IfModule>
# END WordPress
This doesn’t create a subdirectory under which all further blog posts will fall, but it does accomplish my primary goal, which is to be able to easily tell people the URL of my blog, even if the actual blog posts are still in the root directory. Not totally elegant, but effective!
I’d still like to know: does anyone know how to get the blog posts into a true subdirectory?