this post is in reference to Slack/Hipchat/Hangouts Direct Messages, not Dungeon Masters
An all-too-common approach to communication I’ve seen is DM’s for any number of subjects which should be public: how to set up a server, a discussion about an architectural proposal, how to address the content in an open PR, and so on. At best, they limit information sharing among the team members; at worst, they further fracture a team’s cohesion and ruin any efficiency in communication by forcing folks to repeat themselves.
Continued DM’s among individual team members serve only to further cement tribal knowledge, cut folks out of decision-making, and avoid embarrassment for not (yet) knowing something. The practice of direct messaging for non-sensitive discussions should be discouraged, in order to promote healthier teams.