Re: Copyright infringement ?
I've no idea what the NPMs terms are, but publishing content against an author's wishes seems more significant than withdrawing content because it has a name that clashes with that of another, unrelated, product.
And in the time it took them to write that PR statement, they could have written their own implementation of "left-pad" and published it under the old name and version, avoiding any legal or ethical issues around restoring the original code.
Ah, well. Maybe this will be an object lesson for people who use NPN, and maybe it'll draw some well-deserved ire down on Kik.