In seriousness, the posting of a blue message in a message dump is proof to leadership and fellow members of the faction that you're actually out doing things. I'm all for people posting RP as well.
Message dumps are like a Faction Diary, which have the added OORP function of providing the player base with an inner history for the faction and explanation for actions. (What a character says to the person he kills is probably different to what he says to his superior).
Message dumps therefore serve an ambassadorial role, and are a tool for recruitment. (People may find things they like in the faction or its philosophies, or simply want to join a busy faction).