grammar - Use of が vs を with transitive verb, 受け入れる（＋もらえる）

This is probably fairly basic but, not being a native speaker, I'd like to confirm if my understanding of grammar of the following sentence (from 中上級日本語, Feb'14) is correct and what is natural.

In the following sentence I would have expected the subject to be the speaker and the object of the transitive verb 受け入れる (to requite), to be their feelings (気持ち), however their feelings take が and are therefore the subject:

失恋：私の気持ちが相手に受け入れてもらえないこと。

Is this possibly because もらう is in potential form (?) or is it possibly because the sentence is nominalised by こと (?) what is the norm here and when would を be appropriate?

Notes:
1) "An Introduction to Adv Jse Spoken Jse" tells us that for expressions of desire，mentioned in the comments, for the ~たい construction が is "normative" but "を" is also used in actual conversation.
2) Makino's Dictionary of Basic Jse Grammar tells us that for ~たい　form of transitive verbs either is fine but が is preferred if the degree of desire is high (perhaps a similar principle applies here?).

Answer

There are probably people that teach that が can only mark subjects. I don't like that theory, since it makes it really hard to explain some other things.

So I will proceed under the assumption that が can also mark objects of stative verbs (adjectives like 好き, verbs like 分かる, the ～たい form and the ~える・れる potential form etc). In fact, it seems that が and を are in competition in these positions.

りんごを食べたい - りんごが食べたい

I personally prefer the が version, but it seems that many speakers (mainly younger ones) like the を version.

In the given example, I personally like を better, and I think it's because 気持ち is not really the object of the stative verb もらえる, but of 受け入れて (i.e. 気持ち attaches to 受け入れて before the whole thing attaches to もらえる).

[気持ちを受け入れて]もらえる

But I suspect that for some, the power of the potential form is so strong that it forces the が. Or maybe they parse it thus:

気持ちが[受け入れてもらえる]

Sorry for the vague answer. But in many cases, different native speakers will use particles in slightly different ways.