Changing default function calls on Beta fails the challenge: Bug or Feature?

Just finished the Palindrome Checker on the Beta. To test edge cases that I could think up, I plugged various parameters into the default-provided statement that calls the function palindrome(str) at the end of the editor. Then I proceeded to waste half an hour wondering why my code wasn’t passing the tests (given that up until now (based on my console-logging output), it looked like the testing suite called the function with the provided parameter twice. DO NOT DO WHAT I DID. Or rather, once you are sure your function works, copy your code to a text editor, reset the code, and paste back only the function. It passed on the first time.

For those who are contributing to the Beta, is this a bug or a feature? Should we tell campers about it? I have a very high frustration tolerance. Chasing that feeling of stamping out a bug is like heroin to me (I assume - I have never done heroin). However, not everyone is like me, and I can see this being an issue. Maybe put it in the intro, or in an FAQ, or maybe not require the editor-provided function call in the tests?