Slashdot does this to some extent. Moderators are invited to choose from a small subset of tags. The most used tag by the moderators is listed next to the comme

Slashdot does this to some extent. Moderators are invited to choose from a small subset of tags. The most used tag by the moderators is listed next to the comment's karma. Your idea would be a generalization of what Slashdot does, and it certainly has merit.