It's good to know that others struggle with the auto-scrolling problem, as well. I don't think I've seen it mentioned in any of the other chat-related threads.
Not having unread messages pop up to the top is probably why some of my guildies never respond to private chats. If they have more than several chats in their list, they won't even see it without intentional and persistent scrolling.
I'm still on Android 4.4.2 - it's an older device for testing my development apps.