Comments -Caveats * Relative urls will *not* work - How fix?

I have the comments extension on a production site.

I can add the comment, hit submit, but I get /commnets page cannot be
found error

I have looked at a bunch of things.

As the it says:

== Caveats

  • Relative urls will not work on comment pages if they fail
    validation, since the page gets re-rendered
    at a (probably) different level of the hierarchy. Always use absolute
    urls and you won’t have any issues.

BUT…

Where do I set the qualified URL ???