Instructions are clear

2 years later... description updated! :-)

Did you read any of the intro comments within the sample test section?

running sample causes errors but submitting passes all test cases?

"www.xakep.ru", no prefix "http://" nor suffix ".com"

Just a guess, but "markers" can actually be more than 1 character.
Sadly this does not explain the error completely cos' you do escape the markers.

why do I get an unknow error?

why does the ordering of the duplicates matter?

I want to give crap for those edge cases... but I understand that they are day to day stuff we have to deal with, so I wont. Only one thing tough, there is one case that has you modifying the function chunk argument. That should already be taken care of, for the simple reason that the function definition appears by default, and most people don't think of changing any of that, at the assumption that the author created it correctly.

So, either remove the complete function definition or eliminate the case when no chunk size is entered. It could be left if the feedback from the test cases were more accurate but in my case all I got was that process took way too much time to complete, it never told me anything about missing arguments.

I agree. I think that at least should be 6 or 5th Kyu. The tests cases put an pretty good emphasis on performance.

Edit:
My bad, no performance issues here, just that the feedback from the test cases is all messed up in those invalid chunk size edge cases. It always says process took too long. I would suggest to pass those test cases upfront, and just leave the random ones hidden.

yup. this kata was pretty challenging. one of the test cases was "this kata easy" and far from easy

Is this sarcasm?