Recently, I found a question on Arqade that was similar to a question on the other site on the network. From my experience, duplicates between the whole Stack Exchange network are not possible. Is it allowed to quote the answer to the similar question and post it as a answer to the question on Arqade, quoting it and linking to the original question?
I personally do not see any problem with this, as you are giving attribution to the person who originally wrote the answer on the other site. If it is a long answer however, I would only quote the most relevant parts and if possible add a little detail of your own. Quoting from another post on a different SE site is not really any different that quoting from another source.