I have tried this on both my phone and my MBP for over two years and I just can't seem to get used to it or to easily get through replies, especially when there are multiple I hadn't checked. It's just a mess trying to find the trail. Even opening the last one and scrolling down through seems like they repeat. Trying to reply to one and not the others is also frustrating. I finally went back to the old school view, I will call it the Outlook view, just separate entries for each reply. In concept, it seemed like it would be useful, but unless I am doing something wrong, I found it so confusing. Do others "group by conversation on their phones and is there a setting or a trick that I have not come across in the last two years to make it useful? It's especially confusing on iOS.