This is only a minor annoyance, but it would be nice to have resolved.
When normally looking at your inbox, if you delete a message, the selection moves down to the next item in the list. However if I sort by sender, then group messages and collapse groups (this lets me delete all messages from a particular sender in one go), it then moves up instead of down when I delete.
If I’m cleaning up a folder, I have to hit del to delete the group, then arrow down to the next item rather than just hit del again. If the group is expanded rather than collapsed though (and I usually expand before deleting to check the contents), after a delete the selection jumps up two items up rather than one, so I was having to hit del, down, down, etc to tidy things up!