Background (what you would like to be able to do and where):
In regards to the undo/rollback/thank setup, I don't think putting rollback on the overflow menu is nessecarily the best idea because usually the advantage of rollback compared to a regular undo is the speed of it. On the other hand, people worry about accidently using the tool when they don't want to. People will sometimes customize their watchlist on desktop to get rid of rollback for this reason (see Wikipedia:Customizing watchlists#Remove or modify the rollback link). That was my main concern with the variance in the button placement on whether you're reverting an IP or another registered user as it's possible that mistakes are more likely to happen that way. I understand your point about how having everything together would be crowded, though. Maybe some way of customizing it in settings would be helpful? Or making the buttons vertical instead of horizontal? Something like 'undo' and 'rollback' for IPs and 'thanks', 'undo' and 'rollback' for registered users? That way, if someone accidently presses something, it's more likely to be undo instead of rollback - @Clovermoss

Feature summary (what you would like to be able to do and where):
Have consistent placement of undo, rollback and thank button in the diff view in the Android app

OR

Change the UI elements of the button so it is more clear

Designs: