A friend worked on a project in 2005 that had lots of K code in production. They had a contract with Kx Systems and Arthur Whitney in particular because, in my friend's opinion, only Whitney could really understand K code well enough to debug it. Friend's description was it took my friend two days just to comment the code into something grokkable by a normal developer, whereas AW didn't need to do that. Of course, it took Whitney those same two days of staring at the code before he said "Oh, of course, how silly of me." and found the bug and all resolved.

Part of those two days of commenting was that since K is interpreted all of the developers would hand-obfuscate all of the code so that the variables were a, b, c, etc. so that they would be slightly faster to parse than a multi-character string. This sort of thing is done all the time now, with JS to make it load faster, but his team at least didn't have any scripts to automatically turn developer-friendly code into interpreter-friendly code, they worked with the interpreter-friendly code version.