@elkaki @feditips @ernest My guess is that you can comment and upvote, because “favs” from Mastodon should translate to “upvotes” in kbin. But since there is no “dislike”-button in Mastodon there is nothing that would translate to “downvote” in kbin, therefore you cannot downvote a kbin post via Mastodon.
However, there are fediverse platforms that have a dislike button, like for example friendica (which I am using). Dislikes from here may be translate to downvotes on kbin, but I haven’t tested this.
To you other question: you can follow the magazine by copying and pasting it’s url into the search field of your mastodon app. This way you find the magazine in mastodon are able to follow it.