Monday, June 2

coldturkey.sh

Place in /etc/cron.hourly or equivalent:

 #!/bin/bash

 if ! egrep -q '^127.0.0.1 reddit.com' /etc/hosts
   then echo "127.0.0.1 reddit.com" >> /etc/hosts
 fi

Escalation may be warranted.

(Addendum: You probably don't actually want to use the .sh extension. run-parts is likely to ignore files consisting of other than alphanumeric characters, dashes, and underscores.)