That chart is, for news organizations seeking to tame their commenters, perhaps the best evidence yet that adding a few obstacles for those seeking the leave their mark on a web page can actually lead to more comments. And better ones, too.

That chart (bigger version here) tracks the number of comments left by month on the Gawker Media blog empire, Nick Denton‘s collection of themed sites (Gawker, Gizmodo, Deadspin, et al.). It covers September 2005 to the present. See that big dip on the right? That’s when Gawker implemented a new, stricter commenting system, in which trusted commenters get preferred access to readers and the unknown hoi polloi have to audition for an audience. (We wrote about it at the time; in an internal memo, Denton wrote about “taking back the site from some commenters who thought they were in charge” and said “we’ll be able to encourage the kind of discussion that *we* want — not one that is dominated merely by the most prolific of our commenters. It’s our party; we get to decide who comes.”)

In essence, Gawker’s “class system” means unknown commenters get stuck behind a “show all discussions” link few users will click. What most readers will see are only the musings of trusted commenters and the few comments from the riff-raff that either Gawker staff or trusted commenters have decided to promote — the “featured discussions.” (The system also put the most recent comments on top, not on bottom as at most sites. That would seem to reduce the possibility that a dumb early comment would sway the chain of comments that follow it into irrelevance.)

As the chart shows, the shift led to an immediate decline in comment volume. (Interestingly, the biggest drop seems to have been at Jezebel, Gawker’s women-centric site. Attention communications and/or gender studies grad students: There’s a thesis somewhere in there!) But comments quickly rebounded and have since skyrocketed at a much faster slope than before the switch. Some of that is no doubt related to Gawker’s overall increase in traffic, but the scale of the increase is still remarkable.

Gawker Media CTO Tom Plunkett posted the chart on his blog. His interpretation?

Quality *and* growth — it’s possible! We launched tiered commenting mid-year 2009, and introduced a new process to manage comment volume. Note the dramatic drop in volume, and the subsequent rise (double in 9 months). With this increase, Gawker still has the best commenting system/experience out there — and I usually hear the same from people that want to share their opinion… Though there were some calls to do so, purging commenter accounts is not a solution for the out-of-control commenter community. Nor is a large moderation staff. We believe pruning, and a commenting platform as we have implemented, will lead to increased participation, while at the same time encouraging quality. This data, and the subjective opinion of many, seem to back this assertion.

I’m a regular Gizmodo and Gawker reader (and less regular Lifehacker and Deadspin reader), and I can add to the subjective opinion that average comment quality is higher than before. But “better” isn’t the only scale on which you can measure comments. I think the audition-for-an-audience nature of the new system also makes the comments quippier; Gawker comments can feel like a bunch of wannabe Henny Youngmans spouting one-liners and seeking attention. But that vibe may have more to do with Gawker’s content and tone than the details of its commenting policies.

In any event, complaining about awful commenters seems to be the first thing any gaggle of journalists does when lamenting the new news reality. The default solution has been to say every commenter should have to use his or her real name — a solution with practical as well as ethical problems. (Although Facebook Connect may be taking away some of the practical concerns.) Still, there’s a whole world of ways a news site can improve the tenor of its comments while keeping itself reasonably open. Gawker Media’s success is one example of how.