I would prefer it if once I set my chosen account and theme settings, they were then tied to my account and remained even if I log in on a new device. Or even if I log out and back in. I am getting tired of having to reset the theme and other settings.
I leave pages open when I am reading long manga. If I leave one open overnight, I often find that I am no longer logged in. This usually shows up when I hit the end of chapters and jump to the manga page, only to find out it hasn't tracked all the chapters I have read.