Hi Lula, you are right there are analogies. Even if I use Damus I didn't know the logo before today with the new release, when I see it on the top of the app! However the two logos are quite different a recognizable, Damus is flat, the proposed Amethyst is 3D. I dubt you can confuse them, don't you?
I'm quite more worried about Obsidian one: https://obsidian.md I just remembered it and it certainly inspired me without realizing it.