Should DF support rel="canonical"? Reply to topic

I can see this being useful for a number of modules, where the same page is accessed with different URLs, for example in the forums with access by post id or topic id.

Also in any module where the latest content is displayed by default so the the permanent url can be canonical for when it is replaced by the next content.

I think I will use it AD to make the short url canonical.

Did anyone use this or have any thoughts?

Useful. The question is the best way to implement it on DF.
Adding a new global var $can_links to the header so each module can add their own duplicates urls? As metatatag or pagetitle?