I thought there used to be a way to set a thread tag for Public to be able to post in it. The need arose today when we had a random player accusing a guild member of ninjaing an epic in a pug. They said they had a screen shot to prove it but we couldn't have them post it because you have to be a member of the site to post.

There is no way for anonomously post, if that's what you mean. In order to post, the account needs to be created first.