I’ve been browsing the [feature] tag for a while, and this is a great use for the subcategories suggestion:
This post should have some visual indicator on the pages linking to it that it’s already done & completed. It’s really short (only two posts), and the window for any ‘action’ has really ‘expired’: it’s a feature request that’s accepted and completed.
http://meta.discourse.org/t/add-meta-tags-og-tags-etc-to-allow-embedding-discourse-articles-in-other-sites-e-g-via-embedly/1036
However, I cannot in good conscience suggest one of these same indicators for declined [feature] posts due to the hilarity present over here. 
TODO mockup screenshot goes here