I have encountered this situation a few times (for example, https://mathematica.stackexchange.com/questions/42110/parallel-computation). Typically, someone quickly posts a comment mentioning related posts or even indicates the question is a duplicate. I am not sure if it is considered helpful to answer the question in this case.
Pros for giving an answer
It benefits the OP. Because the related question is typically not identical to the one asked.
When people search for a solution, the more posts, the more likely a solution is found.
Cons for giving an answer
Duplicates effort (but what if I just want to take a rest from work?).
Discourages people from searching for answers before asking.
What's your opinion?