Not sure if it’s a bug but posting here in case it is:
If you switch Home Kingdoms, are you supposed to lose your Revenge battles? I’ve fought one or two Revenge battles out of a list of three, switched home kingdoms, then when I went back in to the Revenge battle screen, it’s been cleared out - I lost the remaining two or one battles.
Not a bug as far as I know. Like your hometown is attacked, if you switch your hometown to a new place, this new place hasn’t been attacked, so no revenge.
It has been like that forever, so I assume it is deliberate. Unlike old versions, there is currently very little need to ever switch home kingdom, so it won’t happen too often.
Oh yes there is. I choose the kingdom of which traitstone variety I’m running out of.
I didn’t realize there was an option to turn every kingdom on at once. 
I understand the thinking of this, but if I switch back to my original home kingdom, the Revenges are still lost. So is that part a bug or also expected?
Like MarvelKit, the reason I am interested in that I only have one kingdom up to 2 stars for the double or whatever bonus tribute it gives which helps the best between log ons, but would like to fight my Revenge battles in a kingdom where I need traitstones. So while switching to another kingdom causes losing the Revenge battles to show up, if I switch back, then they should re-appear is what I would think.
The server won’t log individual kingdom stuff like revenges, so once they’re erased they’re gone.
It seems you’ll have to make a decision between kingdom bonus and trait stones. Least now we have a reason to choose our kingdoms again, so that’s something.
Also, by “2 stars” do you mean 1 Gold Star or 2 Gold Stars? Because the second gold star only grants you +50 gold per day, which isn’t worth swapping kingdoms for.
For the moment my home kingdom stays in Forest of Thorns, because strangely enough I always lack minor nature stones. I have plenty of every other minor and major colours, where the minors are far outnumbered by the majors.
Ah, it’s 2 Gold Stars for the +50, I mis-read the Double Tribute at 3 Starts as though I already had it instead of it coming next. I guess I’ll just switch then and not worry about the tribute for now.