Allow me to digress a bit, 許してください
I do not totally object to the use of romaji. In some instances when one person wants to make a point about a particular word/phrase without going the hassle of switching to another IME, the romaji may be appropriate. But if the beginner student starts to learn romaji without paying much attention to the formal writing systems of Japanese, then you've got a problem. Kana and Kanji helps the student by allowing the students to visualize the words. It wouldn't be of help if all they can remember is how a word's romaji appearance is like.
Also, for more complicated sentences, romaji is not appropriate. An example would be a play on word, such as the sumomo one and the niwatori one. Obviously the meanings of those phrases (albeit a bit meaningless) are much more easily extracted from its kana (&kanji) versions. I think most of you know what I mean already.
Regarding using Japanese to learn Japanese:
Sometimes even the native speakers don't speak proper Japanese and thus there are many books on such topics as keigo and advanced bungo etc. For more advanced grammatical patterns, it may be easier for a learner to learn from a Japanese book since the book may present definitions using simpler Japanese patterns that one, by that time, should have already had a grasp on. And sometimes there are words that are really untranslatable to another language, which makes understanding the words rather difficult by studying via another language since the author must use the word in a context that he/she sees fit, to show as an example. But, if the word already has a Japanese synonym which expresses the essence of the word, then much effort would've be saved.
I do not totally object to the use of romaji. In some instances when one person wants to make a point about a particular word/phrase without going the hassle of switching to another IME, the romaji may be appropriate. But if the beginner student starts to learn romaji without paying much attention to the formal writing systems of Japanese, then you've got a problem. Kana and Kanji helps the student by allowing the students to visualize the words. It wouldn't be of help if all they can remember is how a word's romaji appearance is like.
Also, for more complicated sentences, romaji is not appropriate. An example would be a play on word, such as the sumomo one and the niwatori one. Obviously the meanings of those phrases (albeit a bit meaningless) are much more easily extracted from its kana (&kanji) versions. I think most of you know what I mean already.
Regarding using Japanese to learn Japanese:
Sometimes even the native speakers don't speak proper Japanese and thus there are many books on such topics as keigo and advanced bungo etc. For more advanced grammatical patterns, it may be easier for a learner to learn from a Japanese book since the book may present definitions using simpler Japanese patterns that one, by that time, should have already had a grasp on. And sometimes there are words that are really untranslatable to another language, which makes understanding the words rather difficult by studying via another language since the author must use the word in a context that he/she sees fit, to show as an example. But, if the word already has a Japanese synonym which expresses the essence of the word, then much effort would've be saved.