Ask HN: What constitutes plagiarism in open-source?

I recently have been called out for plagiarism in a Reddit thread.

https://www.reddit.com/r/programming/comments/17tccsc/comment/k8w5o26/?utm_source=share&utm_medium=web2x&context=3

I shrugged it off the first time it popped up, because in my eyes the person making the comment is more sour that I am impeding their ability to monetize the concept by making it open-source than they actually believe that I cloned their work.

However, the same user then started spamming my project users with their messages about this project being a clone of theirs without proper attribution and going as far as to double down by posting a new thread on /r/programming once again stating that it is a clone.

https://www.reddit.com/r/programming/comments/17w3toy/comment/k9etf1x/?utm_source=reddit&utm_medium=web2x&context=3

I saw this thread a few hours late, so by the time I got to respond everyone already had their pitchforks out. Bursting out a few responses in panic probably didn't help either.

Anyway, that's the context. The projects in question are https://github.com/zerostep-ai/zerostep and https://github.com/lucgagan/auto-playwright. I added a section to the documentation using every concrete piece of evidence I could think of to prove that these projects are as distinct as they possibly can be given the narrow scope of the problem and possible ways to implement it (https://github.com/lucgagan/auto-playwright#addressing-controversy).

I also think that, in retrospect, it would have been nice of me to acknowledge that their project was a source of inspiration for Auto Playwright. However, at no point did I copy their project, so the thought of LICENSE attribution did not even cross my mind.

I am trying to be cool head about this and think of what is the proper response. More importantly, I am trying to get a perspective from folks outside of the original debate to see if I am wrong with my actions.

Is copying parts of README enough to call for attribution to the original project?

Is copying error message enough to call for attribution of the original project?

Where is the line?

I still think this whole think exploded because I effectively released something that provides comparable functionality to a commercial solution that they are working and thats what spurred this debacle. However, I also acknowledge that I am struggling to reconcile dozens of people calling me "** code thief" in private messages and my sense of righteousness, which is why I would appreciate the insights.