Hi sgull
... because I didn't think it would be necessary for me to get a notification when I post or reply ...
Read it again:
"Turn notification on when you post or reply to a topic"
It says that if you reply to a topic, it automatically turns on notifications for that topic, so you'll be notified when others
post to that topic.
When posting, under Attachments and other options check the box labeled Notify me of replies
When reading a topic, there is a Notify button next to the Reply button