RELATED IDEAS
Create a discussion with a teammate Group
Today, to start a discussion with a group of people, you need to type out each of their names to add them as participants. This can be cumbersome when the intention is to start a discussion with a large group of people. A possible solution customers have asked about is using Teammate Groups as a way to invite people to discussions en masse.
Open question - do the participants of the conversation need to stay up to date with the members of the Group?
In response to your open question "do the participants of the conversation need to stay up to date with the members of the Group?"
I personally don't see a reason for this, especially if that reopens old conversations to the new member's inbox. If groups were also taggable, retag the group to add all current members to a discussion.
Follow up suggestion, allow groups to be taggable in conversations. I know why it doesn't currently exist, but most teams (in my business) are 3-8 people. Most of the time, we know exactly who to tag & ask questions to. But sometimes, we don't. Sometimes we just need to throw the net out there & see who bites. Sometimes a message is urgent and we just need anyone to respond.
Optionally: For convenience, directly next to a group tag - if you're part of the group that's been tagged - add a selection of some sort to "unsubscribe as a participant." It can either be a button explicitly worded as such, or as simple as an icon with hoverable help text.