Last night, I did a little experiment. I made
a post that contained some data about the differences between the British and American versions of the HP books, and intentionally said nothing about what I thought fanfic writers should take from that. I hit post, and then watched to see what would happen. I guess you can say I wasn't surprised by the response, though I will admit to being a little disappointed.
Commenters seemed to fall into a few different groups. One group looked at the information, said, "Interesting", and then engaged in discussion in (sometimes long) threads about why the books were different and debated the validity of making such changes. Those threads were interesting to follow, and though they got heated at times, for the most part people were making reasoned arguments and backing them up with evidence. Implications for writing fanfic came up in the process, of course.
( But there was another group of people whose comments frankly left me baffled. )