What the hell is so alien or uniquely Japanese about that?
Nothing many cultures and people have codes of honor, my problem with the question is; I can't answer whether he is honorable or not unless I know what standards of honor to use. If asked is he honorable by the standards of bushido, Eight Precepts of Bhudism, or the code of chivalry; I could answer as to whether he is honorable or not. To answer the question I kind of need a measuring stick to judge him by (in this case a code of conduct). (Though I could and did also use personal opinion which is that he is amongst the most honorable person in the manga which isn't saying much since most are fairly dishonorable).
Had the question been is Ranma lawful? I could answer it since I know the laws to judge him by (no he is not very lawful ignores several laws entirely like those concerning theft, private property, and trespassing).
Had the question been do I find Ranma to be moral? I can answer that as well. Since I have my views of what is moral. Though I can't answer as to whether he is moral by Japanese standards since I don't know enough about what is considered moral and immoral by Japanese standards.
Fine, suppose I admit that there's some sort of moral encouragement of rape here within your examples--which I don't-- but suppose I do, then what? This goes nowhere towards proving giri ninjo and gimu should be used specifically in Ranma fics instead of western equivalents.
First, Why did you put in moral encouragement? Socially acceptable or honorable does not mean moral or even lawful.
The only reason giri, nijo, gimu, bushido, eight precepts of bhudism, etc... should be used instead of western equivalents is because Ranma is not western. He should be judged by his own cultures standards which he would be familiar with, instead of by foreign standards. It is possible for him to be honorable by foreign cultural standards but it should not be expected of him since he is not part of those cultures. Similarly he should follow Japanese law since he is in Japan even if the law is different by western standards (like the age of consent you would not expect him to follow the US law -18 or the german law -14 or icelands 15 you'd expect him to follow the Japanese law -13).