Someone who has gone and clicked through his/her E2 hard links (or those of others) - one hundred nodes worth. This allows the links to show up as soft links on the relevant nodes (though you'll have to go back and forth to create those soft links, since it's not as facile a process as it was on E1). There's no list of top linkers, since it's pretty much a private, anonymous process, and I only noticed a few minutes ago that I became a C-Linker sometime last week.

While Noding for Numbers might be a bad thing, Linking for Numbers is a good one - it leads to a more fully-functional Everything. Now I'm working on becoming a D-Linker, and then an M-Linker.