There was no recent (in the past one month) thread asking for this feature that I could vote for or add my comments to, so I started a new one.
The problem is that sometimes a question requires many steps to solve it, and there are many answers, say one which gives all the necessary steps and the solution but you do not understand some steps in the answer, and another answer after reading which you completely understand the first answer, but this second answer does not contain all the steps and the solutions. Sometimes, answers have hints to solve a question, and often you get a better idea to solve the question after reading all the answers.
It is not fair, in my opinion, to mark one specific answer here. Ideally, I should be able to mark 3-4 answers, if they all helped me substantially and are quality answers and there is no single answer which alone would help me to solve the problem.