I think it's worth considering that application development and GUIs really aren't K's thing. For those, yes, you want to be pretty careful about the concept of

I think it's worth considering that application development and GUIs really aren't K's thing. For those, yes, you want to be pretty careful about the concept of a "character", but (as I understand it) in K you're more interested in analyzing numerical data, and string handling is just for slapping together a display or parsing user commands or something. So a method that lets the programmer use array operations that they already have to know instead of learning three different non-array ways to work with strings is practical. Remember potential users are already very concerned about the difficulty of learning the language!