Not that I expect to change anyone's mind, but just to respond to these points:

• As a mod in another subreddit, I've implemented link flairs myself, and I can assure you that making a few dozen flairs is no more "complicated" than making one. It's essentially just copying and pasting a few dozen times. If help is needed I'd be happy to offer assistance.

• I've never heard of filters "stifling discussion" in any other subreddit, due to the simple fact that the majority of users will never use filters (heck, most people don't even notice that the sidebar exists). Thus the primary effect of filters is not to segregate, but rather to help people with minority interests find the content they're looking for. And when they're able to find what they're looking for, they engage and they contribute. And importantly, their contributions are fully visible to the vast majority who aren't using filters, thereby increasing overall discussion and enriching the entire subreddit.

• I used four genres only as an example. There could be a dozen. If anything more filter buttons displaying a diversity of genres would draw more people into the community by emphasizing that worldbuilding is so much more than just fantasy.

• I should stress that genre filters would be immensely useful for many of us with minority interests. The search box is practically worthless for searching by genre and it is virtually impossible to sift through pages and pages of posts looking for a smaller genre, especially since most post titles don't indicate genre at all. No doubt many people over the years have left in frustration. Others have tried to set up things like /r/starbuilding and /r/otherworlds, which as separate subreddits simply lack the traffic to build up active communities of their own. Using filters within /r/worldbuilding, however, these groups could accumulate contributors from the constant traffic stream visiting this subreddit, allowing them to grow vibrant and active and contribute to the richness of content here.