In „Why does the use of microtype and xfrac lead to a high compile time?“ the comment seems to provide the best answer. If seen this also in other questions. What is the best way to accept it as answer?
The usual approach is to post a comment asking the person who posted the information to convert it to an answer. I'll do that.
I fully support Joseph's answer.
If we do that, sometimes the comment poster doesn't create an answer though, perhaps because he didn't read the request or he doesn't care.
To not let the question unanswered, it would be ok then that anybody writes the solution as answer, after some time and referring to the commentator, which can be accepted then. We often posted such answers in community wiki mode, as nobody earns reputation and other users could easily improve it.
Such examples where I did it: