난 네가 좋다 means I like you. In Korean, it is not absolutely necessary to have the subject. So you can also say 네가 좋다. Nevertheless, it is not redundant to put 난 there. 예의 없어 보여도 네가 좋아 means I like you even though you look impolite.

"난 네가 좋다" => As for me (난), I like you (네가 좋다) => I like you. 난 (나는) used like this is very common regardless of whether affection is involved. The topic part (난) sets the high level scope (it's about 나), and the rest acts as a predicate clause. This way, you can say complex things in a more direct and compact structure. 1 돈이 없다: There is no money (a little vague but usually taken as "I have no money"). 2 나는 돈이 없다: Speaking of me, there is no money => I have no money (clearer). 3 나는 남동생은 있지만 여동생은 없어: I have a younger brother but no younger sister. In #3, the English version has brother and sister as objects of "have". In the Korean version, they are like subjects, marked with 은 and having their own verbs 있다 and 없다. That's the essence of such topic-subject arrangement. You can talk about some attributes of a given subject as if they are the subjects themselves, in the foreground with a subject-like immediacy. And if the context makes it clear, the topic part 나는 can simply be dropped without changing in the rest of the sentence. It is one of the distinctive elements of Korean which don't have an analogue in most European languages.