I have seen many people brandish their own shot on XXD XD at whatever ISO and say it looks fine. People shouldn't do that because shot to shot there are always variations due to lighting conditions etc. What looks great in 1 shot at ISO 6400 does not mean the next shot in a different setting will look just as great....
[TL/DR version] That is sort of the point those posters are trying to make and why they're asking for examples from the OP so that those types of variables are able to be evaluated.
[Longer version, if you're bored at work, like me]
This is true for ANY body...just because one person can't get a shot that they are happy with out of it doesn't mean that the model line is bad. Those pic posts you refer to get made as proof that a statement such as "The xD/xxD/xxxD/xD/XYZPDQ has bad/poor/faulty high ISO performance" are false, as stated, without more qualifying info that normally gets left out. Many people get perfectly good results with any of the bodies, at any of the available ISO settings for that body; regardless of manufacture
The individual photographer may find it easier to get the types of results they are looking for, under the conditions that they shoot in, using a specific body or set of bodies; but that in no way means that another body is bad.
Just because a Corolla doesn't hit 180mp, whereas a Porsche can, doesn't make the Corolla a bad car. It has a different use/purpose.