I could be wrong - but I'm not seeing anything that will help search engines index kbin.social effectively. There is a loose robots file, but I'm not seeing any indicator of site maps. Pretty much a necessity if you want to get crawled automatically.
A bang just hands the search term from DuckDuckGo into the search field of the target website.
Safari suggested kbin as a search engine as soon as I loaded it up so it is definitely not a big matter to add it. I'd really enjoy to see this as I use bangs A LOT