Comments
Comments on a Ghost site are Ghost's own feature, and they are off until you switch them on. Once enabled they appear at the foot of every post, tied to your membership system — a reader signs in as a member to comment, so there is no separate account, no password, and very little spam by construction.
Neutrino positions the comment section within the post layout and passes it your accent colour and your light or dark setting. Beyond that, the theme cannot style it. Ghost renders comments inside an isolated frame, which is a deliberate design on Ghost's part — it means the comment system can be updated without any theme breaking — and the practical consequence is that comments will not follow your corner style, and will look subtly like Ghost rather than entirely like your site.
That is a platform constraint rather than a gap in the theme. It was investigated and consciously left alone: reaching inside another product's frame relies on internal details that are not a public contract, and would break silently on Ghost updates.