[Sashimister]

Originally Posted by berrypie

Sashimister さん(and others who'd like to discuss and teach me), I'd like to discuss the verb+行くin here, よろしくお願いします！

Verb + 行く ＞＞＞　Verb + いく. Good writers do not use the kanji in these phrase.

However, if you look carefully, this applies only to the first of the four groups that I introduced to you. In the other three, there are no verbs immediately before the いく.

Originally Posted by berrypie

Although it's not too hard, it still takes me a while to understand this.
In this case, I guess it implies the meaning of "ongoing" and "keep doing something"?

Precisely, just as I titled this usage (動作の継続・進行).

ずーーーーーーっと～～していく。　= You keeeeeeeep ooooon doing something.

I am a bit confused here.
Comparing with 納得する, I guess 納得がいく & 満足がいくmore emphasizes on "understand and accept".
For the last one, I understand what it means, but I guess one can say "心まで" too? (or may be I am wrong, because I've heard of 心から)

In the first two sentences, the subjects are 納得 & 満足, respectively. If you were thinking that it was a hidden "I", that would have made it difficult for you to understand the sentences.

These two sentences talk about your 納得 & 満足 "reaching a satisfactory level" or not. This "reaching　or not reaching there" is being expressed by いく/いかない.

Regarding the last sentence, no, you cannot use 心まで. It must be either 心行くまで or 心から. One can say that 心 in this context, means 満足.

In this case Sashimister has used the expression 訳にはいかない. I guess it's the same as "いかない" except the former one sounds softer. (As in ～わけではない to ～ではない)

Wrong, that is if you're saying that you can replace the 訳にはいかない by いかない.

Just think of ～～する訳にはいかない as an idiom meaning "There is no way I can ~~."

And ～～しない訳にはいかない as an idiom meaning "There is no way I can do without ~~ing."

It's not hard to understand these, but it's a bit difficult for me to understand how it sounds like. For example, how does it sound different if I compare the first sentence with よし、この方法でしましょう。

この方法でしましょう is grammatically correct but it sounds so bookish that you will rarely hear a native speaker say it, especially with よし, which is highly colloquial.