I notice a number of questions in the HP and LotR areas (just because they're the ones I focus one) get answers containing links to the respective wikis that exist for both of these universes. I was wondering if SFF.SE should consider a bias towards quoting primary sources, i.e. the books in those cases, rather than copying and pasting an answer off a wiki that might just be someone's rampant speculation?
It's a balance.
Primary sources are 100% more preferable.
Why? Wiki could be wrong, though not overwhelmingly likely. Either someone there screws up or inserts their own opinion. Slytherincess can give many examples from HP by heart, I ran into a couple myself.
Wiki as a source is 100% fine, when it clearly and explicitly sources from primary material:
"Foo did Bar, in episode 'Forgotten Plot Device #3' of 'Cancelled for being awsome' show. As evidenced by this quote:
Insert picture of Foo doing Bar
Wiki as a source is ok, if it includes a general source, but no quote.
Wiki as a source is somewhat OK if it doesn't have a precise source, BUT you clearly state that "The wiki doesn't source this piece of info". Especially if you can confirm from your own memory that the Wiki is correct despite not having the primary source to quote from.
Wiki is tolerable if it doesn't have a source, BUT you really should include the disclaimer that you can't find an exact source on the Wiki (I try to do that).
Wiki becomes less OK if 100% of the answer is quoting an unsourced Wiki. Not grounds for deletion or downvotes, but not really a very good answer, and I would prefer a sourced one to replace it.
Why? Because, while a Wiki can be wrong, it is not wrong all THAT often, so an answer quoting a Wiki is infinitely preferable to no answer or idle speculation.
A primary source is great, but sometimes it's faster and easier to type up an answer from a wiki -- and even then, often, the wiki is citing an episode of a TV show or a scene in a book. In my case, I don't do eBooks, so it can be harder to dig out a book than to link to the Wiki (which may even quote the book). And for video, like film and TV shows, it's also easier to link to the wiki for support rather than pull out a DVD. (And I often may cite the scene after having just watched it for proof, but still link to the wiki.)
So I don't think it's always an either/or situation. Sometimes the Wiki points us to where the answer is, or we can cite it for facts we may know but can't immediately document. (For example, if someone asks what color a Vulcan's blood is, we may not remember the first episode that is stated, but can find it easily in a wiki.)
It's absolutely fine to have a personal bias like that (I share this to a certain extent,and try to do it in my own answers).
The way that you indicate this is that you vote up answers that do contain these references. I guess if you feel extremely strongly about it, you might down-vote answers that don't have the references (leaving a comment to indicate why), although that seems excessive to me.
You can also edit answers to include references to the primary source (or post an alternative answer if that's more appropriate). I wouldn't do this just to replace a link to a wiki, but I do if I feel that it will strengthen the answer, and that it was likely that the original answerer would have done so if they had the material at hand.
It is notably more work to get references to an original source. With books, you can pull quotes from Amazon's "Search Inside" in many cases (and from Google's equivalent in many fewer). However, it's still much more work, and this can't be done with every book. If you have an electronic copy of the book, this is considerably simpler (searching and copy and paste!), but, especially with older books, this isn't particularly likely.
TV episodes and films are even more difficult. As far as I know, there isn't any legal equivalent for scripts (e.g. a "Search Inside this DVD" on Amazon), although that would be awesome! That means you're stuck with transcribing yourself (requires access to the material, it's slow, and it's a lot of work) or finding a script/transcript online (which is almost certainly illegal).