When you want to make a world you need to make an world name, but when i make a world and then copy it like 5 times the name will be bigger than that is possible. I made some screenshots to let it see. Sorry if this is not a bug.
MCPE-73766
When you copy an world you'r world name will be infinite (Sorry it is intented)
Resolved
Invalid
0
I think this is intended. Making a copy of a world will add "copy of" in front of the world name each time you copy it.