While I don't know how to disable smilies, I have figured out the answer for your problem with 'n' - http://moodle.org/mod/forum/discuss.php?d=67108#301865
Let me know if you need some help with this.
Thanks,
Matt
Glossary
How to turn off smilies in Moodle 1.7?
Αυτή η συζήτηση κλειδώθηκε κι έτσι δεν μπορείτε να απαντήσετε σε αυτή.