Thanks, I guess.
I don't understand the rational behind jumbling up a group's email addresses as a consequence of creating subgroups. I'm sure many of my groups' members would also be confused by it, and I don't want to have to try to explain and justify these switcher-roos, so I doubt I'll every permit subgroups to be activated.
If subgroups must be:
subgroup[at]mygroup.groups.io
rather than change the address format, groups should start (and remain) with:
main[at]mygroup.groups.io
I favor the simpler:
mygroup[at]groups.io
and
mygroup.subgroup[at]groups.io
Consistency of form is more understandable and feels more reliable, which (to me at least) is most desirable.
Michael Pavan