I don’t know why this has been downvoted. This seems on-topic for lobsters.
You could also use this source from Lobste.rs, available here: https://github.com/jcs/lobsters
And avoid Arc completely.
Yeah. One killer feature of Lobsters is email notifications, which is useful at the start when users aren’t in the habit of visiting your site. The HN codebase could be modified to support this, but doesn’t provide this feature out of the box.
(I’m active on the Arc forum; come ask us questions anytime.)
Other features that I like about Lobster compared to HN
(1) MarkDown in comments
(2) Tags and ignoring tags.
(3) Private messaging.