Bug or filling feature?

[Lennart Borgman]

Why does fill-paragraph in org-mode produce something like this:

  bla bla http://some.where/ bla bla bla
                 //bla bla

The // on the second line was added by fill-paragraph and is aligned
with that on the first line. I did not change any setting. Or at least
I do not think I did. I did a customize-save-customized however, to
save another totally unrelated setting.