d7 (the Proprietor) does not claim ownership of Content you submit or make available for inclusion on The Seven-Sided Die (the Service). However, with respect to Content you submit or make available for inclusion on the Service, including without limitation comments you post to the Service, you grant the Proprietor world-wide, perpetual, irrevocable, royalty free, non-exclusive, fully sub-licenseable license(s) to use, distribute, reproduce, modify, adapt, publish, translate, publicly perform and publicly display such Content (in whole or in part) and to incorporate such Content into other works in any format or medium now known or later developed.
But what does that mean?
Most importantly it means that I can do the usual day-to-day blogging things involving comments: I can publish your comments in my blog and edit comments that contain seriously problematic content like flamebait or huge layout-breaking images. You retain your copyright over your comments, so you can still do whatever you want with your comment elsewhere.
The "perpetual license" part means that the copy of your comment that you submitted here can, for example, be archived elsewhere, translated into Sanskrit or DoubleSpeak, included with a post in a print blogging anthology, or appear in the hypothetical relaunching of this blog as The Eight-Sided Die With Extra Awesome, and you can't remove or restrain my ability to do those sorts of thing once you've submitted your comment. The point is to make it possible to do new things with the whole content of this blog, comments included, without tracking down each and every commentor for permission first.
(License text thanks to Jonathan at The Core Mechanic.)