Just in case it wasn't clear from all the replies here, using an unknown rel-attribute on links doesn't do anything, and since the default behavior is to use links normally, this just treats links ...

Any WordPress plugin that is involved with user generated content and links may have to update their code in order to support the new code. The WordPress announcement ...

Google updated their rel canonical documentation in order to clarify how Google handles the extraction of rel canonical annotations. The clarification is not meant to ...