From people on Reddit: Something that blows my mind- but is fully true "Hell, I've been in fucking EVE Online alliances that had better opsec than this." "I'll raise you one: I've never been in any EVE alliance that didn't have better opsec than this." ..I noted Board Games(Secret Hitler, for example) require better opsec. So do card games- it's mindblowing to note this too... [Main comment by me - technical outlook]…
The fact that Signal was used is less concerning to me personally than the fact that they had this group chat outside of the overall safety umbrella of fully end-to-end vetted systems.
Though the use of Signal is still concerning in that any official system they would otherwise use would have (one would hope) made it far harder if not impossible to accidentally leak the conversation to a random third party.