Pan places the cursor at the top of a followup message by default if the
user has no signature file defined.

Steps to reproduce the problem:

1. Run fresh install of Pan, with no configuration changes other than the
minimum necessary to read posts.
2. Click on a message and press the follow-up button to reply.
3. Note that the cursor defaults to the top.
4. Now create a signature file.
5. Under user configuration point to the signature file.
6. Press follow-up.
7. Note that the cursor now starts at the bottom of the post.

The default behavior should be to start all follow-ups at the bottom, even
if the user chooses not to define a signature file.