vmstan, PSA: If you're a Mastodon user visiting a kbin site and see something you want to reply to, you don't have to have an account there to participate in the conversation.
Click on More > Copy URL to Fediverse > Paste it into the search field of your Mastodon instance > Interact just like any other post.
All because of the power of federation and ActivityPub! :masto_dance:
Screenshot of "Paste into search"
Screenshot of kbin post as Mastodon result
Screenshot of reply window.