I've inherited administration of a server (and I am not really an admin) and unfortunately there are a ton of things I've never been exposed to.
All of the parameters in the sshd_config are commented out. ssh is working fine however. Does this mean that a default configuration is being used? What is the reason that the previous admin may have done this?
Yes, it means default configuration is being used. There is no particular reason, which can be connected to blank sshd_config. May be previous admin was debugging some sshd issues.