If you wanted to make high-impact fediverse software, I would recommend making a simple daemon that does the following:

- Consumes RSS/Atom feeds
- Posts them as subscribable feeds over activitypub
- So dead easy you can host it yourself as a simple daemon on your server
- Optionally: collects replies as a comment section with a way to render them inline, a-la disqus, with some simple moderation tools. Simplest way to reduce spam would be to make it approve-only to show up on the feed.

You could extend this to allow posting on other servers etc. But, in other words, let more people use the static site generator they already have

The simpler, the fewer dependencies, the better. It doesn't need to be fancy. It could be Guile and sqlite, for instance (and you could use Hoot for rendering the comment stream). Something hackable but low-resources.
@cwebber may it be done in PHP?
@rodolforg @cwebber It could; I've written a set of posts on how to publish over ActivityPub from PHP, and they take inspiration from a post about a single-file PHP implementation.