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?
Dán digaštallan lea giddejuvvon, it don sáhte šat vástidit dasa.