Reward messages in magento are not coming from database. They are not coming from configuration in admin. They are not set in blocks nor templates. So where are they then?
If you want to change the reward message open up the reward.xml file in
your theme and look for lines like this one:
<action method="setRewardMessage" translate="message" module="enterprise_reward">
<message>Submit a new tag now and earn %s once the tag is approved.</message>
</action>
Cheers