Sortinghatchats was a passion project between myself and one of my best buddies, K, from college. There's actually a whole tumblr, if you didn't know, where we sort things and write up explanations and such (and a very active brilliant tumblr community (they also have a discord) that does further analysis and sorting in that same theme). And we also have a podcast
https://sortinghatchats.castos.com/ (also on Spotify, Apple Podcasts, Audible, all that jazz...) where we sort a canon in the lens and talk about our analysis.
We basically started the system because we kept saying things, like good 90s kids we are, like "mmm that character is so Hufflepuff" and then we wanted to understand what the other person
exactly meant by that. It's really just the two of us desperately loving to define our terms. We probably discussed and defined for over 100 hours before we actually wrote anything down, and then we started with just big long descriptions of each primary and secondary house, and the general system, and then doing sortings as examples. And that's all we had for years, until I stumbled upon "ink" which is what the SHC quiz and Stay? are both written in; and it let me have enough flexibility to really write a quiz that felt more like a conversation. Because straightforward point-based quiz doesn't work for this system -- you've got to be able to argue with it a little and do some self analysis.
We didn't employ any specific psych techniques, other than ideas like "ideal types" as part of our conceptualizing. K has a sociology background, so that definitely colors things. But with psych, you'd want to do, like, research, to make things viable and arguable, which obviously we didn't do. So it's just as scientific (not very) as Meyers-Briggs or Enneagram, and slightly less than Big 5, which we think is funny.
The podcast is on hiatus right now, for Personal Reasons, but we're planning to get back into it when Personal Reasons are in a stabler spot. It's a nice way to carve out explicit time to chat with each other monthly. They're good Personal Reasons! All going in good directions, there's just Stuff we have to Do before podcasting makes sense for us again.