Since wp 2.7, wordpress has introduced the paginated comments feature. I've read that this may not be good for SEO as the main content gets "duplicated" on the pages of the comments.
Then I've read that to prevent this, we can specify the canonical URL in meta tags.
Now i've checked the source of my page and a canonical url is automatically added and reads like this on the pages of the comment:
<link rel='canonical' href='http://localhost/wp16/?p=3657' />
So am I cool? I shouldn't worry about dup content? This is actually from the twentyten theme and I am not sure if this feature (the showing up of the canonical meta) was recently added or was always there.