On the other hand, Tumblr would probably argue that their lack of comments is a major component of what has fostered a community worth contributing to and commenting on.

Tumblr feels very safe, very supportive. The lack of native comments yields the social equivalent of a long hug. Words are cheap and comments are easy and they can create an environment of base interaction and mild paranoia. Not only does Tumblr disallow these negative contributions, the only system interactions it does support are overtly positive. Like the high-school art class you’d escape to between classes, everything we do here is wonderful. Everyone’s watercolor gets to be tacked to the wall. You don’t want to tell us who you are? No big deal, we don’t even have profile pages, that’s how little we’re worried about stuff like that.

You could interrupt this by being a jerk in a reblog, but since a member’s primary representation of themselves is a chronological, public display of every contribution they’ve made to the community, you’d have to be a real SOB to make a habit of it.