Hubs get 'featured' by adding them to topic-oriented pages on HubPages.com with a link back to the hub in question. Whether they track clicks-throughs or not, I assure you redirects are not involved.
There are only two (legal) reasons someone would use redirects on the Web - for handling a temporary moved location (a.k.a. 302 redirect) and for permanently moved location (a.k.a. 301 redirect). Anyway, back on topic...
The Facebook button shares count change you have noticed is caused by FB changing their button script or overall API. Not once have I observed changes in the Like button count... like a couple over a month, both varying greatly from each other.
As for the sub-domain question - simply put, Google loves ranking at the top sites with well organized content because it provides positive user experience (bet you this is something you won't hear at a SEO "conference"). Using sub-domains as a site-wide method for breaking down the topic of a site (HubPages in that case) and using properly H1, H2, H3, etc. headline structure in page context is one of the rules of thumb for well organized content. I assume this doesn't make things 100% clear, but hey - what I am supposed to do with just 1282 characters more :)
To break it down - the folks administering this great site have done their SEO job in an excellent manner. The capsules for each hub are also meant to rise the SEO score of your content, so just sit back, relax and publish making use of all those great capsules. And avoid using nofollow when citing sources on your articles.