Note: groups.io will be down for maintenance this evening, starting at 11pm Pacific Time (6am Tuesday 8/3/2020 UTC), for up to two hours.
I am also concious that the more "individual" notifications that thereThat's in the group's Hashtags page already.
The member sees a Mute/Notify button (grid view) or link (list view). That brings up a page where the member can choose whether to receive the related notifications by email (Mute or not) and choose to opt-in to Web/App notification (immediate "push" notifications).
Members who've chosen the Following Only setting for Message Selection (the Advanced Preferences panel in their Subscription page) will see Follow/Notify instead.
This raises another issue; someone chooses not to receive informationThat's an interesting case. If it was they themself that did the edit I'd say no notification is needed. The only other option is (I think) that a moderator did the edit. I would want the member to be notified in that case, you and other group owners/mods may disagree.