Thanks for the extra context, Gerard.
Allowing solutions on group messages feels like a bit of an accidental feature, but I understand better why you were relying upon it now, and I see evidence that others were doing the same in those linked features.
Given that, I’m thinking it may make sense to make it more explicit to enable this feature in the solved plugin with a new like allow_solved_on_group_messages (bool, default disabled) or allow_solved_in_groups (group list, default empty).
The latter would also address Enable solved plugin for specific groups inboxes
I’ll see what others think about these options or other alternatives.