I'm not sure if this should be filed under bug...

Go to: Blog settings > URL
Choose: Absolute Path
Enter something like: http://yourdomain.tld/blogname (without a slash)
Click Save

-
Then it now shows a warning:

WARNING: it is highly recommended that this ends in with a / or .php !

Focusing on the slash only.

It is actually better to 'not' have an ending slash like so:
http://yourdomain.tld/blogname

than to have one:
http://yourdomain.tld/blogname/

When loading the URLs in the browser:
Setting without slash
a) http://yourdomain.tld/blogname - ok
b) http://yourdomain.tld/blogname/ - ok

Setting with slash
a) http://yourdomain.tld/blogname - 404
b) http://yourdomain.tld/blogname/ - ok

Not sure if it's on my settings somewhere, but if it isn't on my end, then bringing up to the attention. ^_^

Best Regards