But that's not a good assumption to make
I don't see why not. The replying person is usually answering a specific question like how to do a quick and dirty translation from CYMK to RGB, or how to bash 8859/1 into UTF-8. Your answer ought to be short and to the point.
It is then up to YOU (and you alone) to apply this into whatever it is you're doing, complete with appropriate checks and validations. It is nobody's fault but your own if you blindly copy stuff from The Internet (anywhere, not just SO) and paste it in and think "job done".