I am wondering about what the best course of action would be when one encounters an answer which provides the mechanics of a non-trivial solution, but which is presented in a highly confusing way. In particular, in some cases, I feel capable of filling in the details myself and reworking the presentation of the post, but feel that this would be an inappropriate use of the edit system (since, if I were bringing the post to my own standards with no concern for the author, I would rewrite everything). However, since I'd have no new mathematical ideas to add and could not write a new post without relying on the previous answer's contribution, it wouldn't seem quite right to post a new answer (even if it differs entirely in presentation from the previous one) - especially in cases where the answer is deep enough that, poor presentation or not, it is the important result of the question.
In such cases, I would leave a comment on the answer, suggesting various improvements, but it's doubtful to me that the user would change their post - it could be a big change to execute. I am thinking that, after giving them an opportunity to revise (i.e. waiting a day or two), I'd post a shiny new community-wiki answer, using the same idea, but with a different presentation.
Is my current plan acceptable? Is there a better approach?
(This question previously referred to the first revision of this answer; happily, it has been improved a lot by the author, so the above would not apply to it - I guess waiting was worth it. I have since deleted my comment on the post)