That thread does not indicate that an issue existed, rather an error had been made, which, when rectified, sorted out the op's problem.

You can do the same and continue to use auto filtering.

When I send a link from Firefox, new email is automatically created within Pegasus, Copy Self field is on, but the message is not copied to Copies to Self folder.

edit: I've double checked and this is actually an extended issue. It happens randomly with some emails. So, not only FF links don't work, but even new emails from within Pegasus are randomly not copied to Copy to Self folder.

After a quick search it turns out to be an auto-filtering issue:

http://is.gd/AYl1sK

To be safe I'm turning auto-filtering off from all my folders. I'm wondering then when auto-filtering become useful...