This seems an ideal situation for decentralisation. Initially all you would need to be able to do is comment/upvote/answer questions over all sites. Kbin isn't too dissimilar, where you can start a thread that can be voted up/down and commented on - that can be installed across multiple servers, and a user on one server can follow a "magazine" on another (here for example you might follow @meta@codidact.com from elsewhere - and you'd see all the questions and be able to answer or comment on them). It would keep groups of communities separate but still interoperable, and if a site goes offline then the content is still visible from another federated instance. It would also not be necessary to create an account on every server hosting the Codidact software, and comments from other Fediverse/ActivityPub accounts would work too.

Yeah, my big preference is that I can use a single account to interact with a bunch of these sites. Certainly, there are benefits to having additional accounts, but for most things I'd like to just manage a single profile.