It is difficult to see who is included in a group direct message.
e.g A user messaged me and 4 others. The default ad hoc group name is a list of the six individuals.
The very long group name displays as somewhere between one and two and a half names individual names across desktop and mobile.
Currently, the only way to identify who is in the group is to initiate editing the group name.
One possible solution:
Display who is in a group DM as an auto generated first post.