I have kakoune installed with Nix, and I’m using alacritty, but can reproduce the issue on kitty too.
When opening a new kak instance, all the characters that aren’t letters are not rendered correctly in the UI elements:
I could switch to using kakoune obtained from the arch linux repository, as the issue doesn’t show itself there, but if anyone could help me get it working from nix it would be amazing. Thanks everyone!