Concensus on やりもらい動詞

Question

In this post, I insisted that AはBにしてもらう is synonymous to BはAにしてくれる but not necessarily to BはAにしてやる / あげる. However, there was a counterargument that says you can't use くれる unless the speaker is involved, which doesn't seem reasonable to me because you can say things like 花がきれいでいてくれてうれしい.

It also says that AはBにしてもらう is rather synonymous to BはAにしてやる / あげる than くれる, but that doesn't seem reasonable either.

1. 先生になんとかしてもらえないか聞いたらどうだ？
2. 先生が何とかしてくれないか聞いたらどうだ？
3. 先生が何とかしてやれないか聞いたらどうだ？

To me, the one who Sensei is to help seems the listener or someone closer to you than sensei in #1 and #2, but someone else than whom Sensei is rather closer to you who belongs to the other side of you the speaker, the listener and Sensei in #3.

What are your thoughts?

Answer 1

The comment "you can't use くれる unless the speaker is involved" is correct. In the case of 花がきれいでいてくれてうれしい, the receiver of the action is the speaker. The action is きれいでいる, the agent is 花. The speaker is using the personification to express his/her happiness as if the flower was being beautiful for the sake of him/her.

The difference between ～してくれる and ～してもらう:

森くんは僕の引っ越しを手伝ってくれた。

（僕は）森くんに僕の引っ越しを手伝ってもらった。（"僕は" at the beginning can be omitted.）

The both, the agent of the help is 森くん and the receiver of the action is 僕. But when くれた is used, 森くん should be the subject of the sentence. On the other hand, when もらった is used, 僕 should be the subject.

Another important difference is, くれた doesn't specify if 僕 asked the help to 森くん or not. But もらった indicates that 僕 asked the help to 森くん.

So, let's see the examples you put:

1. 先生になんとかしてもらえないか聞いたらどうだ？
2. 先生が何とかしてくれないか聞いたらどうだ？

Even though I don't know the context, these two sound reasonable. The both end with "聞いたらどうだ？" so the students are thinking to ask the teacher to do something (to resolve the problem), but the first gives the impression that they themselves want to resolve the problem and that's why they want to ask the teacher for the help.

The second gives the impression that they are depending on others.

3. 先生が何とかしてやれないか聞いたらどうだ？ To me this doesn't sound fair.