Why are there ® marks next to the names of some commenters?
In 2005 the Clarks opened up the site to unregistered commenters for the first time. This move was made with more than a little trepidation. Among their many concerns were trolls and spammers, but chief among the potential problems they saw on the horizon was the potential for identity theft. That is, they were worried about some miscreant deciding to post malicious comments under the guise of an established member of the community. For example, there was nothing in place to keep Joe Schmoe from moseying on in and posting as E. Christopher Clark.
The ® mark is a sort of badge of authenticity. Wherever you see the ® mark, you can be sure that that comment was posted by the registered user in question. It’s possible that a registered user will forget to login before posting an “authentic” comment and will therefore not be given the ® mark, but you can’t win ‘em all. That’s why the Clarks encourage all registered users to login before posting comments.