This kind of system appears in quite a few games as a means of helping to remind the player of what his next goal is. The most famous examples are the fairies and Midna from the 3-D Legend of Zelda games. The player can talk to these characters at any time with the press of a button, and get either helpful advice or a pointer in the direction of the next plot event. However, the characters in Dragon Quest 8 are much more interesting than is typical because they do more than just give the player generic reminders of where his next destination is.
What makes the conversation system in DQ 8 interesting is that it is both event-sensitive and location-sensitive, in a addition to the typical plot-sensitive nature of these interactions. The other characters change what they depending on where the party is and what just happened. For example, if the player takes an optional detour to visit a fortuneteller, the other characters will talk specifically about the advice that fortuneteller gave. If the player wins a victory in the monster arena side-quest, the party will talk about how good victory feels, and so forth. The characters even say different things on the overworld than they do in towns. The system is remarkably responsive to changing situations in the game.
Unfortunately, a problem with this is that sometimes, the other characters don't have anything to say at all, and all four of them just say ".........". In other words, the characters were not given any written dialogue. It happens surprisingly often, including an entire dungeon relatively early in the game. This lack of consistency is glaringly obvious when otherwise the game rewards the player for talking to his team with lots of witty dialogue.
At least the ability to talk with my comrades at any time helps alleviate the problem that some of them very rarely have speaking roles in cut-scenes. At the point I am at in the game, Jessica and Angelo in particular have barely said a voice-acted word since Angelo was recruited. While they have been developed somewhat through the optional conversations, it has left those two characters woefully under-developed and somewhat one-dimensional so far. It is also making me wonder if it is possible to completely skip recruiting Angelo or turn down Jessica's request to join.