So I have these strings:
I know how to replace all duplicate characters, but that's not what I'm after. I don't want Balloon to become Balon, for example. I only want to replace if the full string is a duplicate, such as DDuupplliiccaattee becoming Duplicate... Keeping Balloon and Noodle as they are.
I think you are probably looking for something like this:
\b - matches start word boundary
((.)\2)+ - match 1 or more groups of duplicate characters
\b - matches end word boundary