dontconvert2islam tries talking Quran, who is morally accountable?

In answer to the video "Worst Creatures in Islam"

And now this youtuber, by mentionning the issue of moral accountability in the Quran, wants to scratch the top of a great iceberg of Quranic wisdom, then quickly escape after drawing his hasty conclusions. I will not let him. 

In the hereafter Justice will reach its ultimate form where only the Truth in one's actions will be measured

7:8"The weighing on that day is the true. As for those whose scales are heavy, they are the successful".

This verse explains, the counter weight for each action will be a specific standard of truth. For example when one's charitable actions are weighted, their heaviness or level of worthiness in God's eyes will depend on whether these actions were performed in accordance to God's prescribed standards. Each good action will be taken into account indiscriminately among the people 99:7. A good act from a Quranic point of view is something done to please God because it is commanded by Him directly or is in accordance with the principles of His revelation. The Quran repeatedly speaks of how any act devoid of this principle by those who willfuly reject those very principles, will remain "lost" in this present world where the corresponding reward will be given. It will not be accounted for in the Hereafter where the good nature of a deed isnt what validates it in God's eyes. It must go hand in hand with something else, as will be shown later on.

Similarly, believing in Allah does not merely imply believing He exists but believing in Him as is taught by the prophets. These prophets have their teachings revived and cleansed from all innovations, neglect and corruption, inside the final revelation to mankind, the Quran 6:158. The Quran gives many examples, including those of the Christians or Arab pagans who, although declare belief in one supreme God, they do not believe in Him as is taught in the Quran, the reminder of what original monotheism was, despite the truth being communicated to them and their misconceptions cleared. It is to be noted the Torah is spoken of with the same reverence, when it was the absolute criterion/furqan of all moral valuation, of all the fundamental ethical truths 21:48. Anyone claiming belief in God at that point in time, but not as was explicitly taught in the Torah, would not be holding a valid belief.

Having said that, we may now delve deeper into the issue of moral, spiritual accountability in the Quran. It is established that only God knows who was effectively and sufficiently exposed to the truth before willfuly rejecting it. The responsible ones are those who

68:43"were called upon to make obeisance indeed while yet they were safe (saalimun)".

This word indicates full possession of the power of judgement. The Quran states that for individuals to reject the divine guidance while in a state of being "saalimun", this can only happen if the truth conflicts with their paradigms, desires, and worldy interests, and essentially stems out of pride, prejudice and arrogance hence its condemnation. Analyzed objectively and rationaly, Islam can never conflict with one's inner conscience. That is why one always finds an element of subjectivity based on worldly interests, whenever someone with a decently working rational mind rejects Islam after all questions are properly answered within the islamic paradigm. Such people do not reject Islam because they are stupid. If they go through a serious introspection, they will point out those worldly reasons specific to them. No philosophical objection a disbeliever will raise but it will be common to every monotheistic system. There are answers that better explain these problems from a theistic view rather than atheistic. That is why such people will most often resort to objections in regards to Qur'anic statements or ahadith, which turn out to be genuinely based on poor knowledge as well as the desperate need to pile up as much layers of excuses as possible so as to cover for the real, base, worldly reasons for rejecting Islam.

Therefore one only becomes accountable for rejecting Islam

47:25,6:49,4:115"after guidance has become manifested to him"

something the guilty himself will recognize in the hereafter 67:9. This is the central condition for responsible choice of creed

22:17"Surely those who believe and those who are Jews and the Sabeans and the Christians and the Magians and those who associate (others with Allah)-- surely Allah will decide between them on the day of resurrection; surely Allah is a witness over all things".

This establishes that whoever, Muslim or else, follows his religion with sincerity and isnt guilty of rejecting divine ordinances out of pride, prejudice or arrogance, stubborness and unflinshing stance despite the clear explanations, that person will have his sincerity in his own faith judged according to God's knowledge, wisdom, justice.

In fact the Quran when quoting an exchange between the prophet Musa and Firon, explains that Allah alone decrees the destiny of those who were not reached by divine guidance for He alone knows their motives and understands the cause of their choices. He alone can appreciate their spiritual merits and demerits

20:48-55,17:54"Your Lord knows you best; He will have mercy on you if He pleases, or He will chastise you if He pleases"  

15:24-5"And certainly We know those of you who have gone before and We certainly know those who shall come later. And surely your Lord will gather them together; surely He is Wise, Knowing"  

25:58"and Sufficient is He as being aware of the faults of His servants".

God adds to Moses' answer that common sense and the observation of nature must lead a person to a basic cognizance of a unique Creator.