So, I'm coming up with some ideas for my new site, and would like to guage some plausible options, would it be possible to have a checklist on the registration page, that allows them to tick the categories they're interested in, any that aren't ticked become ignored on registration?
This probably isn't a feature request. Can it be moved to the Dev category. 
EDIT: Thanks, also Julian, I don't think the move notification works properly.
I would imagine it's possible yeah, check this plugin out for an example on how to add fields to the registration page and how to read the response on the server side.
https://github.com/psychobunny/nodebb-plugin-registration-question
You'd just need to write code to list out the categories (should be a few places where you can find out how to do that), and on the backend, after registration call User.ignoreCategory(uid, cid, callback) for each category that was not selected
Topic move notification is fixed on master.
