I assume that if today you started work on a second chat adapter, you’d end up copying and pasting a bunch of code from the slack one. That’s the stuff that should live in the core plugin! In particular, the admin page the filter rules. The core plugin would watch post_created, check those filters, then trigger notify_chat for delivery. Any adapters that receive notify_chat would just send it, and not worry about filters themselves.
Not exactly – an admin has to set it up, but it can be used by public chatrooms. For example, if you are in the emberjs slack, you might want to see when new posts are made on the emberjs discussion board. That has to be set up by an admin, but consumed by regular users.
Once the core product is built we can look into layering user level messages on top, but like we said earlier, that’s a whole bunch of work that depends on other stuff working nicely first.