Re-readng the posts this morning and realize I needed to clarify a couple things...
I don't know if anyone knows for sure all the reasons why she did it - the people who knew her IRL on HF didn't really share much on that issue and rightfully so. I think everyone has their demons/battles that they struggle with in life. Based upon what I saw at the time, I'm convinced that the online activity (and that post in particular) was a contributing factor (it seemed to me that the post was likely to have pushed her over the ledge that she was already very close to). You never really know what people on the other side of the screen are going through. It's some sort of ingrained human ego thing to subconsciously assume that everyone else is just like yourself. "If I can handle it, you should be able to as well". Only that isn't always the case (and this is, to my mind, how the issue relates to Derka).
This happened roughly 18 years ago now. I don't remember the username of the one that authored the final bully post, but I do remember that it was not a name that was used on HF. Most of the peeps on that alt site had chosen new names when they moved over from HF (much like some peeps did here in the move from Shaggy), so it wasn't clear who anyone really was.