I mentioned Sadayusa in the earlier thread to which you made reference, and another member offered an opinion with which I largely agreed. I don't know how he broke the tip of his knife, but I received one with a broken tip, and chose to fix it rather than send it back. I wouldn't part with a Sadayusa over so small an issue.
While I have no objective means of measuring hardness, other than feel or glass, I believe the knives to be exceedingly hard. That's one thing I like about them, and something which no doubt contributes to what I perceive to be their other virtues; i.e., they get razor sharp and stay sharp, though they are prone to developing micro chips. I enjoy sharpening these knives more than any others I own.
Sadayusa knives do have a somewhat rustic quality, as was noted, but are well made. I personally haven't detected any appreciable discoloration or odor.
A more professional evaluation would be of general interest.