Direct rebuke vs divine sarcasm ? They are both critical. Elihu said Job's righteousness and unrighteousness don't add to God or take anything from Him. But other men's wickedness can leaven those around them. So, it is perhaps understandable that from Elihu's perspective as an intercessor, a
man experiencing human frailty and hanging out with Job, that he is rather upset about the potential collateral damage to Job and others, if Job carries on down the path of accusing God of injustice. God on the other hand is not subject to human frailty, so can be less influenced by fear of the consequences that may fall upon humans. He also has a long game perspective , whereas men look from a mortal limited lifespan perspective.
The difference need not be satanic vs. divine.
I think this accusation that Job's righteousness is more than God's is implied rather than explicitly stated.
As an example, in Job 29
12 Because I delivered the poor that cried, and the fatherless, and him that had none to help him.
13 The blessing of him that was ready to perish came upon me: and I caused the widow's heart to sing for joy.
14 I put on righteousness, and it clothed me: my judgment was as a robe and a diadem.
15 I was eyes to the blind, and feet was I to the lame.
16 I was a father to the poor: and the cause which I knew not I searched out.
17 And I brake the jaws of the wicked, and plucked the spoil out of his teeth.
(Implication "But God isn't doing that for me.")
Job 30: 9 He hath cast me into the mire, and I am become like dust and ashes.
20 I cry unto thee, and thou dost not hear me: I stand up, and thou regardest me not.
21 Thou art become cruel to me: with thy strong hand thou opposest thyself against me.
22 Thou liftest me up to the wind; thou causest me to ride upon it, and dissolvest my substance.
23 For I know that thou wilt bring me to death, and to the house appointed for all living.
24 Howbeit he will not stretch out his hand to the grave, though they cry in his destruction.
25 Did not I weep for him that was in trouble? was not my soul grieved for the poor?
Job 31:16 If I have withheld the poor from their desire, or have caused the eyes of the widow to fail;
17 Or have eaten my morsel myself alone, and the fatherless hath not eaten thereof;
18 (For from my youth he was brought up with me, as with a father, and I have guided her from my mother's womb
19 If I have seen any perish for want of clothing, or any poor without covering;
20 If his loins have not blessed me, and if he were not warmed with the fleece of my sheep;
21 If I have lifted up my hand against the fatherless, when I saw my help in the gate:
22 Then let mine arm fall from my shoulder blade, and mine arm be broken from the bone.
(But look how God is leaving me to suffer unjustly.)