Perhaps I am a little sensitive to body language and personal space. I actually took a psychology class on the Psychology of Space--personal space, body language indicators, and other body language extensions--and I learned about lots of interesting things that I had sensed before taking the class. This was many, many years ago, so I have forgotten the terminology and facts with this, but the ideas and implications have stuck with me. Fascinating stuff.
Body language comes in lots of different forms--eye contact, personal space, hand gestures, and body posture for a few.
New comers may seem more withdrawn into their personal space--you know, arms crossed, weak eye contact--but over time, they can become more relaxed and comfortable. Their body posture reflects this.
Some group members are highly respected and valued. When they are speaking, the members generally stop, listen, and make eye contact. When Tom talks, everyone listens. When Kristen gives a critique, we are paying attention. When Randy is talking, we are ready to laugh.
Group members that talk too much or do not contribute as much to the group do not receive the same response to the group. In the past--I am thinking of two past members who workshopped their novels and did not spend much time on reviews and then stopped attending when their novel was finished--the group generally recognized the lack of reciprocation. The body language would be more shut off, personal space would not be open, and body posture would close off when these people spoke. As awful as this is, I was less likely to pay attention when these members were talking then when Tom or Kristen or Randy are talking.
The converse is not exactly true for the online groups because the video chats attempt to create a sense of "meeting." But the meeting does not really work to read how others are responding to each other.
In an online writing group, eye contact is not obvious. A writer might appear to be looking at me, but they might be just looking at their screen/word doc/self video. Body posture and hand gestures are limited, too, because we can only see a small window of their body. Personal space and body posture are very limited because most writers are posed to see their computers in the best position possible.
And of course, sometimes, writers may use a photo or image to hide their video. This hides all body language.
Perhaps I sound old-fashioned, but the face-to-face writing groups allow for a plethora of body language that helps us to understand each other and our reactions within the group. Even if we do not understand body language directly or have all the vocabulary to explain this, I think we all sense this.