Some suggestions:

1. Add rel="noreferrer" to the links you inject.

2. I don't think nested anchors are valid HTML. Try injecting your links after the username link, not inside it. And the underline between each icon on hover (in Firefox on HN pages at least) looks horrible.

3. All those icons look messy. Why not collapse into a single keybase icon which maybe opens a tooltip with more details when you click on it?