Having read through the Nifty-serve chat now (ugh what a royal pain that was to slog through >.<;; ), and having seen follow-up from some other posters, I suspect the (non-GH) thread was closer to reality way back when the original doujinshi came out. The thing that is still unknown is what, if anything, will ever come out from what was hinted at in the interview that was done where Ono said she was reworking a previous series (I think that was the gist of that thing), since that comment is the most recent thing to come out. As near as I've been able to determine so far, Nakaniwa Doumei (*the* doujinshi) was supposedly published in 1995. Quite a long time ago.
Anyhow, the stuff in the GH thread started at post 522 in which the poster suggested that the reason nothing came out after Akumu was because it was based on an actual incident. There was an incident where a girl coming home from a school field trip and her family was murdered and their bodies dismembered and that the incident was based on trouble over the property.
Post 523 said that there was no need to explain something that was widely known already.
524: This is the first time I've heard of it.
Are there any actual articles about it?
525: It's not like Ono-san publicly stated that it was based on it, but the gist of things are identical, so people have said a number of things (to her) about it over the years.
You'll be able to find it easily if you do a search for 'murder of a family in Nerima' (Nerima ikka zansatsu).
In the actual incident, the girl wasn't killed~.
It's common for novels to use real incidents as the basis for stories. Miyabe Miyuki's "The Reason" is based on the same incident.
What I've been able to find out is that yes, there was indeed a multi-murder complete with dismemberment of some of the bodies. J wiki link The incident happened back in 1983, and the only info I could find on it in English was regarding the execution of the murderer.
As for the other comment, it wasn't so much in the Nifty-serve chat log so much as in the after word comment about the Akuryou series by Ono Fuyumi. In it, she says:
Now then, as for this, about which I still receive many inquiries.
First, thank you very much for the many threats, pleas, and petitions.
However, the series is on indefinite hold. I'm very sorry to be unable to meet your hopes. There are currently no plans for a subsequent book. There are none, yet there are a number of things (laughs). Eventually, when it's forgotten about, I might write something. In this regard, I'm sorry for being such a haphazard author.
This isn't necessarily the publisher's intent. The publisher would like me to write more, but the truth is that I don't have the wherewithal to do so at the moment. Frankly, I've gotten a bit sick of it. I have to admit, it's tiresome having people say "write this" or "it has to be this way". When I think of trying to force myself to meet these requests, I can't help coming to hate the series. (There have been so many requests to "have Naru confess his feelings" that I got so fed up and thought that if you want it that much, I'll have him confess and kill him immediately after......)
There you go. Ah, the joys of 2ch. ^^;