No.

Be my guest literally suggesting a rewording, then :)

When you began writing the description to the problem you actually seemed to agree with jmossel as you wrote

"(55, meaning -4.2 compared to the average) ... (95, 35.8 more than the average and so on)"

where the signs of the differences are as expected. You then later contradict yourself by writing

"The resulting list/array of differences starting from [55, 95, 62, 36, 48] is thus [4.2, -35.8, -2.8, 23.2, 11.2]."

A tip to improve the description would be to change the first quoted sentence to make it consistent with the second (I would say change the second to be consistent with the first, but that would make all existing solutions to the problem incorrect).

I also don't see how simplicity, beginner-friendliness or empathy with the beginner caused you to make this choice of sign (and to be inconsistent about it in the description).

Do you want me to add it to the list ? :p

non valid sequences forces you to validate the input which is good coding practice :)

Slow solutions don't pass the tests in time already. Even fast ones may not do if the system is busy--my solution got accepted on the second try. What kind of other tests do you suggest?

Well, I wanted to keep it extra-simple (and beginner-friendly, most of all), so while I myself considered that POV when I wrote it, I put myself also in the shoes of someone with zero previous statitics experience, tried to write a user story and create a kata accordingly.

Yet I see your point and if many other people will report the same, I will change stuff. Right now, I would prefer to avoid it, as it would be made on a subjective POV and it would invalidate all the previous good solutions.

I would not call it an issue and I think the description clearly states why the input is wanted that way, with examples and discussion about it.

Any tip to improve the description?