I looked what do that filter and i found this site:
http://adambrown.info/p/wp_hooks/hook/pre_comment_content
So, pre_comment_content is executed before to save a comment in the
database...
And i think to you are right Gareth, this don't should be executed in
magic fields.
The bad thing of fork a project is to also fork the bugs, the good
thing is to we can fix them when we found them :p
I will speak with Hunk (Edgar) and i hope remove this filter in the
next version (we will release a new version in the next week)
Thanks for your feedback Gareth