I program in K professionally and help maintain a fairly large codebase. It's an unusual-looking language and it takes practice to learn to "skim" K code in the way that most programmers are used to for their favorite curly-bracket language, but it can be learned.

The biggest messes I have to clean up come less from "clever" code than they do from people who try to program in K as if it were some other language. For example, somebody fond of for loops might write the following to apply a function 'f' to pairings of values and their index in a list:

    result:()
    i:0
    do[#v
      r:r,,f[v[i];i]
      i:i+1
    ]

Ugly, complicated, but "close at hand". There is of course a much nicer and more idiomatic way to do the same thing:

    result: f'[v;!#v]

Most of the time conciseness isn't the goal, but you get it as a side effect of writing good code and working "with the grain" of the language.