The @ points your browser to the community on the right instance. As for the link taking you to the base instance while on kbin, it's because kbin uses /m/ instead of /c/ as a separator like Lemmy. So for you to visit that NCD from kbin, the link would be https://kbin.social/m/noncredibledefense@sh.itjust.works. Also it looks like kbin is still having problems receiving updates from lemmy and vice versa.