In the Mastering Lightning Network book section 3, it describes the Lightning Network as being "... so much more than the cryptographic protocols on top of the Bitcoin scripting language. It is a comprehensive communication protocol that allows peers to exchange Lightning messages to achieve the transfer of bitcoin. The communication protocol defines how Lightning messages are encrypted and exchanged."
My question is: can Lightning messages be leveraged for purposes other than "to achieve the transfer of bitcoin" (i.e. generalized communication messages)? Can Lightning messages be sent over the network using the LN protocol to an address of, for example, a friend of yours? Seems like the network could have an extendable purpose in this way; however, since I am new to the LN and learning as I go, I'm unsure of the technical feasibility of this.