Looking over some example DCI implementations, they usually contained 'Actor's involved in an exchange, although in the ineligibility scenario all the potential actors (person, participant) seem too passive to be labeled as actors. Ineligibilifier was a contrived actor to fulfill this role (albeit with a stupid name). 

The module is also based on example code, where the actors are 'taught' actions specifically for a given purpose. I understood it as a way to keep actors and actions clearly defined and separate,  and also as a way to group like actions.  (It probably makes more sense when there is more than one category of actions involved in an interaction).