At the current state it's only single-user, but I'm working on a multi-user implementation. It should be available as soon as I have a proper implementation for the ActivityPub Group actor (similar to what WriteFreely already does, where you have a Group @blog actor that aggregates post from multiple Person actors). That would also unlock full compatibility with Lemmy/NodeBB and other threadiverse implementations. But it takes a while to get done right - and a multi-user set up is also a design challenge when your selling point is to have a blog running on a single folder with Markdown files.

About a free instance, it's not currently available (you'll need your own domain and host and then you can just spin up a Docker container), but AFAIK YunoHost is considering adding it to their offering.

There's an example with LaTeX here https://blog.platypush.tech/article/Build-an-open-source-drone-with-a-Raspberry-Pi-and-Platypush

Initially Webmentions and AP reactions were rendered on separate panels (with the Jinja rendering templates provided by the webmentions and pubby libraries respectively), but then I found that a bit confusing and cluttering, because there were basically two comment sections with two different time-sorted lists of threads. But if people prefer the other way around I could also add it as an option or a filter toggle 🙂

So, mentioning you like this shows up in the guestbook? @fabio@manganiello.blog