Is this code one of the kinds of code that WordPress.com doesn't allow? If so, would I suddenly be able to use this code if I paid for WordPress Pro?

There is not upgrade that you can purchase for WordPress.com that changes anything stated here:
http://en.support.wordpress.com/code/
http://support.wordpress.com/com-vs-org/
http://en.support.wordpress.com/domain-mapping/#important-notes-before-upgrading

See here please > http://en.forums.wordpress.com/topic/how-can-i-use-footnotes?replies=2#post-640646

Text.[1]

then:

<id="fn1">1. [Text of footnote 1]↩

But this simply doesn't work when I preview the page in WordPress. Clicking the ↩ will link back to the footnote reference in the main text, but the footnote reference in the main text won't link forwards to the footnote! Is this code one of the kinds of code that WordPress.com doesn't allow? If so, would I suddenly be able to use this code if I paid for WordPress Pro? Or am I using the wrong code? I've experimented with a few variations based on other sites which use this internal linking effectively.
Blog url: http://eeleach.wordpress.com/