This question has been edited so that the question is now a 'guide' to the chemfig package, where before it asked for help with it. Is this sort editing in good style with Stack Exchange or should the question be reverted?
There is another reason for not including an answer in the question: such answer is excluded from the voting process. In this case, since the answer was supplied by the package author, and seems to be of very high quality, it is perhaps unlikely that anyone will come up with a better solution, but it is still possible. The community should have a chance to vote on all the answers and decide which answer is the most valuable. Suppose you need help with something and find a question on SX that is clearly related to your problem. There are two answers, one in the body of the question, and another one, with 50 upvotes. You have no way to tell which of those two is generally regarded as better or more useful.
I see that the question has been edited since this was asked. In its current form (revision 9) then it looks fine to me, though the last sentence is a little flippant.
This looks to me like a happy conclusion. However, I would like to make one comment on the process whereby this was reached. To me, saying things like "good style with Stack Exchange" or "how Stack Exchange is meant to work" are not good arguments and do not serve to get to the desired point as quickly as possible (and with the fewest feathers ruffled). Note that Joseph's comment was about a "Q&A format", which is better but still not ideal. The point is that there is a real reason for following this "ideal format" which has nothing to do with the fact that this place is run on the SE engine. That reason is that someone looking at this question will expect it to be in a particular format, namely Question first followed by Answers, and so will look for information in a particular place. Not finding it there makes it harder for that person to learn. Hence putting the answer in the question makes this whole question-and-answer less useful.
If it were me, being told "This makes your Q&A less useful" (and told why) would make me much more amenable to editing it to make it more useful. Being told "StackExchange says so" makes me less amenable.