Per the Members handbook for Groups.io;
Understanding the Chats feature
In Premium and Enterprise groups, and in legacy Basic groups (those created before August 24, 2020), Groups.io provides a Chats feature that members can use to create and participate in interactive chats on a group’s website in real time. Be aware that:
Group owners determine whether the Chats feature is available in their groups and, if it is, who can create new chats: all members or only owners and moderators.
When someone creates a chat, Groups.io sends an email notification to group members. After that, ongoing activity in the chat does not generate additional email notifications. Members must log in to Groups.io to participate in and monitor chats.
All group members can participate in chats. Groups.io does not provide a “private” chat option that allows chat creators to restrict chats to subsets of group members.
In some web browsers, the Chat page does not display activity in real time. To see new chat content, members might need to refresh the Chat page periodically.
The Chat page does not display any indication that someone is composing a response. Participants do not see that chat activity is occurring until someone actually posts their response.
So, here are my thoughts;
So, maybe if a topic is OT such as this one, Chat would be the best medium? It would not clog up the Topics with unrelated stuff? Or rather than someone say 'PM me', start a Chat. If someone else is mildly interested they can join in the chat to follow it. Makes sense to me if there is no private info being exchanged.