It appears that the only way to theme the "Add new comment" link that appears below nodes, because it has no id or class, is to target ul.links or ul.inline.
Fortunately for me, I'm not using anything else that might potentially fall under that list at the moment, but should I do so in the future I will no longer be able to style the "Add new comment" in a unique way.
Needs review
1.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.