Sorry, but I don't have any hot tips except the obvious ones. First of all, on the first day of class, I take all students' pictures and have their photos, usernames, and passwords by the second day. My composition class takes place in a computer lab, so by the second day, students (26 in this class) are writing their self-introductions, in class, and they're already "checking each other out" as I can see from the course logs. (My students are always first semester university students, and the only ones who know each other are those who happened to have come from the same high schools.) Since the class is a "writing workshop" in a computer lab, I prohibit cell phones, MP3 players, MP3 sites, game sites, emails, and chat programs, etc. If a cell phone rings, a frivolous window is minimized, or a chat message pops up, students must leave the class for those "violations." That is, if the kids interact with anyone, it has to be with me or the other students, and they usually choose the other students .
Their first essay, then, is a Giving Instructions essay (examples HERE will open in new window), and their first face-to-face work is Peer Review of another student's essay in groups of two. The first question on the formal Peer Review Questionnaire is "What do you LIKE about your partner's essay?" By the second week of classes, then, students are already finding a "supportive" environment in which to write. After that, using Moodle they upload their essay as an RTF file which I grade and "edit" and send back to them, also as an RTF file. Then, students revise their essays and upload them for their classmates in the Giving Instructions Essay Forum. To this point, all the emphasis has been on accuracy, the part I grade most harshly.
After students' essays are posted in the Forum, the next assignment is for them to read and respond to at least five of their classmates' essays writing 1000 words total. The emphasis on this assignment is fluency which is graded by word count, meaning 1000 words = 100%; 800 words = 80%; etc.
Students LOVE getting their essays read and responded to, and although the responses are graded by word count, they still put a lot of effort into writing accurately because they know their work is going to get read by their classmates.
In response to your specific interest in using Moodle to teach social skills, the THREAD in response to the IMAX film about Mt. Everest took place in the sixth week of the semester, so there isn't really a lot that took place in the classroom regarding explicit discussion of social skills. I've always believed teachers can create an environment in which social skills mature, but most Mexican kids at the university where I teach have already developed excellent social skills. (In the fourteen years I have taught here, I have never seen a fight—or even an altercation—on campus; it's true!)
In sum, I credit Moodle's forums as excellent places for promoting written interaction among students, and interaction by definition is almost always civil, at least among young university students.