I know this would not be easy, and I first seconded the proposal to set up obstruction measures targetted at spammers.
I am simply saying that it would be nice to further complement these by mechanisms allowing us to increase the overall trust level between legitimate users. It seems to me some form of better identification is needed for that (not necessarily withdrawing anonymity).
Furthermore, if successfull, I wonder if these mechanisms would not be a real plus for the site. But the editors may have other more urgent work to do of course (including fighting comment spammers in the first place).