Other doubts
 

Nagoyankee, another question for you.

甚だしきに到っては、文学の鬼、などという、ぶしつけ な、ひどい言葉を何某先生に捧げたりしていて、これで はいくら何でも、その何某先生も御立腹なさるだろうと 思うと、また、そうでもないらしく、その何某先生は、 そんな千万失礼の醜悪綽名をつけられても、まんざらで ないらしく、御自身ひそかにその奇怪の称号を許容して いるらしいという噂などを聞いて、迂愚の私は、いよい よ戸惑うばかりである。

What I can say is that
甚だしきに到っては、文学の鬼、などという、ぶしつけ な、ひどい言葉を何某先生に捧げたりしていて、これで はいくら何でも、その何某先生も御立腹なさるだろうと 思うと、また (I understand it)、そうでもないらしく、(I don't understand it) その何某先生は、そんな千万失礼の醜悪綽名をつけられ ても、(I understand it) まんざらでないらしく、(I don't understand it) 御自身ひそかにその奇怪の称号を許容しているらしいと いう噂などを聞いて、迂愚の私は、いよいよ戸惑うばか りである。(I inderstand it).
It's so absurd. Because of そうでもないらしく and まんざらでないらしく I don't understand totally the meaning of the sentence.
I'm sorry to disturb you again but this part of kobutori where Dazai makes his own considerations and there isn't the story of Kobutori is creating so big problems.

Excuse me but I'm not understanding your question this time.

What are those "I understand it" and "I don't understand it" in those parentheses?

OK, after a more careful read, I think I now understand your question.

Keep in mind that in this piece, the author employs an extremely under-stated humor as I mentioned last week. In fact, it is so under-stated and meticulously woven into the texture of his narrative that it might not be easy for the non-native speaker to even notice it, let alone appreciate it.

The passage starts out by saying that a first-class author can be described by such horrible names as 文学の鬼 in the media, (which in fact is a praise of first degree as both Dazai and his readers know). Would this author be offended? Of course not. This is where the phrase そうでもないらしく comes in, meaning "it doesn't seem so." On the contrary, authors are generally pleased to be called 文学の鬼. "まんざらでないらしく" means "he doesn't seem dissatisfied with it." The narrator hears the rumors that authors secretly love getting those mysterious titles. Thus, the narrator, who calls himself a fool, gets only perplexed.

Do you see what I mean by "under-stated humor" now? The narrator is simply playing dumb here. Everyone knows that 文学の鬼 is the most desired title for an author.

I start thinking that here the real 文学の鬼 is Dazai himself. I'd like to say that he is simply a 鬼 in his use of the language making hard for not japanese readers to understand everything but if the reading of this story was easy (really esay) I think it wouldn'tattract me so much.
Thank you very much (once again I must add).

Fully agreed. This style of writing is very difficult to produce as well. Make one tiny mistake and you'll end up insulting all your readers.