This was originally reported in PM quite a while ago for security reasons, but I've been having such troubles trying to hunt the bug down that I feel I have no choice but to turn to the forum, if only to not have the ones in the know hog it all to themselves.
Probably related to the implementation of local quality raising by quest givers, there is apparently a bug whereby local water quality can be raised by quite a bit. Again, I'm really not sure exactly what causes it, and there may be other triggers, but it does appear to be somehow, inexplicably related to butchering of livestock, in that it seems that butchering an animal temporarily raises the water quality in the area, sometimes, under some set of circumstances. There seems to be some correlation between the likelihood of triggering the bug and/or the amount of quality gained, and the quality of the animal being butchered. It might also only work in certain places (like, magic map coordinates or something).
I've been wrecking my brain at this for months now, but sometimes the bug triggers, sometimes it doesn't, and I can't seem to decode any pattern to it, and unfortunately it also seems far less likely to happen in a testing environment. So I would ask you all to try it out and see if you can trigger it. Anyone who can deliver any kind of useful information for actually see what triggers the bug will of course be allowed to keep their high-quality water, and depending on the usefulness of the information I'll even throw in a couple of subtokens.
Thanks for any help you can offer!