Ok, thanks. Guess this is another feature that is only on the plug-in?
It looks like because the free/lower tiers don't have plug-ins, wordpress.com have done a simplified feature set with the most essential functions but left a lot of the plug-in's options out.
The WebFinger plugin optionally improves the federation side of things, but I am not a developer so I don't know exactly what it does. Also, I don't know whether its functionality is included in the free/low tier system?