For me there are two reasons people quote:
because someone said something in a very compact, pithy and powerful way
as an appeal to authority
Quotes stemming from #1 are probably difficult to quote mine, because the quote will have to be long enough to give a pretty good sense of exactly what the author originally intended.
Quotes stemming from motivation #2, on the other hand, are tempting to use quote mining, and to use partial quotes at that -- all you are doing is really name dropping to make it look like whatever author you are quoting agrees with what you are saying.
Trying to quote mine for reason #2 when it comes to religious topics is amusing to me, because if your post or comment is intended to provoke dialogue with people outside of that faith, then people outside of that faith do not recognize whatever person you are quoting as an authority in the first place!
We often see this with people saying "but the bible says", or "but the koran says" -- forgetting that to someone who sees both books as collections of historical but not necessarily divine origins, this reference carries no weight at all. Attempting to appeal to authority in this way ends up being circular in that it is only convincing to those that are already convinced.