So, here I was, looking at a Google search on enchanting and disechanting items in Skyrim, and I came across a post on another site about there being a way to disenchant without destroying items. The poster refers to something named "Divayth's Altar", located north-east/east of the College of Winterhold. Apparently, if you travel far enough, you should see a dragon's head appear on your compass. The altar itself works by using a black soul gem containing a vampire's soul - you place both the item you wish to disenchant and the black soul gem on the altar, wait 24 hours, and the item should be successfully disenchanted without being destroyed (the black soul gem disappears).

I can't find this place, and the post on that forum was dated 27th November 2011, shortly after Skyrim was released, so I doubt it was a mod. Does it actually exist? Have I looked in the wrong place? Maybe it exists only after a certain stage in the main quest or a specific side quest? No searches seem to bring up anything else on this location...