I've been observing a very annoying behavior with auto fill; it persist in
the latest org from git, as well as the version shipped with Emacs 24.3 for
OS X.

Consider starting a clean Emacs session with emacs -Q.  Start a new file,
foo.org.  Do M-x org-mode and M-x auto-fill-mode.  Now enter the following
3 lines:
---
---
---

(yes, that's a bunch of dashes).  Now try putting a long line in between
the second and third set of dashes, and wait for auto-fill to wrap the
line.  Here is what I observe:

---
---
This is a long line designed to exhibit a bug in auto-fill.  It's
---almost as if auto-fill thinks the dashes are a comment symbol.
---

Notice how after wrapping the line acquired a leading "---"!  Why does this
happen, and how can it be turned off?

--Leo