What should we do when we find the answer to question A in the answers to question B? For example, this answer is copied directly from another answer on Stack Overflow (exact duplicate), but the question is clearly not a duplicate. Copy and paste the answer? Link to it? Both?
While copy-paste seems most useful to the reader, it sets off alarms in that part of my brain that hates duplicate code.
Copy paste, if not by the original person who answered should at the very least be accompanies by a link to the original answer.
If you have found such a duplicate, without attribution, by someone different, by all means comment with a link to the original.
Note that I say "should" and not "must" - all content on the site is licensed as CC with Attribution Required - this means on other sites. Within the SE family of sites, it is not required, but a nice to have.
I quote the answer, with a link.
Done it many times:
https://physics.stackexchange.com/a/23239/7433
https://physics.stackexchange.com/a/24341/7433
https://physics.stackexchange.com/a/21787/7433
https://physics.stackexchange.com/a/24196/7433
https://meta.stackexchange.com/a/130264/178438
Note that I try to add more meat to each answer. The answers are 'tailored' for a different question, so I add some extra explanation below.
IMO, the answer you linked to is fine, though he could have explained what was going on.
