You asked why there was no swearing - Japanese has very few swear words, so putting swear words into an English translation is very much a judgment call for the translator. If you're looking for a very literal translation of the Japanese dialogue, there'd be very little or no swearing in Tenjou Tenge.
This is an issue of complexity. It is true that Japanese contains few swearwords. But the
intent of the speaker needs to come throught in the translation.
Kono yaro iterally means 'this guy/person' but it's a sure bet that when someone says that their intention is 'this arsehole' or something similar. The same goes for
kisama and many other spoken terms and words. In this case, it is not so much the verbatim text that matters, but what the speaker intended.
I don't know how much this conceptual problems in translation occurs, but I think it a common problem when translating languages with entirely different origins (ie. German to !Kung or Korean to Swahili). It's not so much that the Japanese have less feelings, it is simply that their language does not allow for such displays of emotion. A literal translation of Japanese (less colourful & emotional) into english (more colourful and emotional) and will therefore almost always lose at least a third of its meaning, which is integrated also into the terms of address and the manner of speaking (more so than english in most cases). The honorific a speaker uses will include information on the speaker and his/her relationship to the addressee, but a literal english translation is simply Mr/Miss/Mrs X.
A verbatim and literal translation from Japanese into English would end up with a very bland and cold text. This may be fine if you're translating 'dry', impersonal text like medical or scientific reports, but will almost always fail when translating manga, which consist almost entirely of spoken texts.
