Signatures on posts, but not comments, seems like an adequate compromise to me.

I'm strongly opposed to signatures on comments, because the basic failure state of "Everyone has a 1-line signature" would dramatically increase the signal:noise ratio on a normal thread.

I'd also be very strongly opposed to any sort of commercial endorsement. "flattr me" is pushing the bounds here, but "you can read my other works here" seems acceptable. An actual shopping link (such as "You can buy my unrelated-to-LW novel here") would make me uncomfortable.