A participant: one who participates in an activity.
A subject. Perhaps it's a little off the beaten path, but a subject subjects himself or herself to an informative medium. They then become informed, and the information informs them (i.e., changes or affects them in some way).
What you describe is a form of interaction or interacting. There is not yet a word, however, for an interactor, except when the word applies to the InterActor which is the medium of web conferencing. Look here and here for possible ideas.
By the way, auditor is a perfectly good word, although its primary application is to the hearing process at work in a speaker-to-audience event or relationship (or more technically, rhetor-to-auditor event or relationship).
Even "further out there" is a dyadic event, in which two people are communicating electronically (assuming there is an interactive component to the communication). A telephone/cellphone/smartphone conversation is a relatively simple medium of informative communication. One person sends information while the other person receives; then the roles are reversed in a sort of ongoing feedback loop.
Not knowing the media to which you refer, I'm at a loss to know what kind of interface there is between the informant and the person being informed. In our electronic age, the possibilities are virtually endless, not to mention mind boggling, especially for Boomers like me.
Finally, there's the good old dialogue which, again, in our electronic age is no longer simply a face-to-face interaction in which people are dialoguing with each in person without the aid of any electronic medium whatsoever (unless you consider to be electronic the electrical activity of synapses firing in the bodies of the people who are dialoguing).
In conclusion, perhaps you could give us more information about the media of which you are speaking and how they/it function(s).