Lets put some stuff straight. The question has a fundamental problem, which is that that question doesn't have a single correct answer, but a long tail of "things that may or may not apply to you", which may have something to do with the edit that was done after it was answered which left it in its current state, the original question could be solved by just searching for a Windows installation media and installing Windows over Ubuntu, but that doesn't work for everyone.
So, to remove Ubuntu you just have to remove the partition and configure the bootloader or install X (I tried to have a self answered question about "How to uninstall an OS?" on SU, but it didn't end well) and hope that the X installation routine takes care of stuff. There isn't a preparation to speak of that is not a generic "do backups of whatever important information of your system, if any", which is applicable to every software removal.
Lets put it this way:
Two users want to remove Ubuntu to install X, one of them just used Ubuntu for 5 minutes and decided that is not his thing, what is the advice you could give him? He could probably just start the installation process of whatever he is going to replace Ubuntu with, make sure it takes care of the bootloader and partitions and done. There wasn't any preparation to speak of, right?
What about a programmer for 10 years? First of all, you would expect him to know what they are supposed to do, but lets presume they don't. If you give him the same advice as above, you probably need to find some exorcist to dispel all the curses that that user threw at you after losing the file which is Good Code™.
I don't think is not a good question not because Windows, but because is fundamentally flawed in the way people would (and did) answer it: what specific preparations have people to do before removing Ubuntu is extremely dependent on the user habits and whatnot, and probably doesn't go beyond "backup" and install X however you are supposed to do it. There isn't a single correct answer that would apply to 70% of the cases for the first part, and the one that does (backup your stuff) is just too short for the Q&A to actually work out.
If the user had asked "how to migrate my personal files on my /home to a X installation?" that would be interesting and answerable, with different tactics that they could follow (for this specific case, Windows creates a english and localized directory of anything under your %USERDATA% (I think that's how its called the variable that points to your user directory), so just copying the directories over should suffice, presuming you always use the home subdirectories that xdg creates).
And just as an extra food for through, the people that finds the question thinks that is more unhelpful than helpful according to anonymous feedback, and the most upvoted answer is an almost 50/50 leaning towards helpful. Take it with a grain of salt, because despite of having 450k views, the total score of everything doesn't reach the 1k votes, which I suspect that people don't even bother to leave any feedback at all, because that's not what they are looking for.