I guess it depends on the people. So far in DF I've always said hi and always got a bunch of "hi"s in return. Though that might be my new player enthusiasm. Can't really talk much during the actual instance since I need to keep aggro, so the only form of communication there is setting numbers on mobs (which sometimes goes ignored) and discussing boss tactics.

As far as FATE parties are concerned, the two I've been in were all very mute and the only thing discussed were FATEs, party organisation (pls inv so and so) and people asking for a raise.