Before Stack Exchange, I participated in a similar site. That site had a requirement: all answers must be different from each other, and users cannot copy content from anywhere including Internet.
I will not copy anything here either. I always try to write everything by myself. If I use other's words, I'll make it a quotation (I already know how to do this). But my question is: are there any penalties here if anyone does copy his/her answer? Does every answer have to be unique (not copied)?