Was the happiness of Kauravas in heaven an illusion?

Question

According to the Mahabharata, after entering the Svarga (heaven) with a human body on Indra's invitation, Yudhishthira witnessed that Duryodhana "was seated on a beautiful throne and he shone with the splendour of the sun and around him stood in attendance the goddess of heroism and other entities of righteousness". Yudhishthira found this insufferable and reminded the dwellers of Svarga about his sinful deeds.

Following that, Narada smiled at Yudhishthira and explained that Duryodhana had suffered for his sins, and that ultimately, Duryodhana was a warrior who had defended his dharma and fought bravely and valiantly, having been a great ruler, a true friend, and a terrible foe.

Was the happiness of Kauravas in heaven real or an illusion?

Narada words indicates that the happiness of Kauravas was real, i.e: they have some sins but also they have good deeds.

Answer 1

As I discussed in this answer, Mahabharat was not a battle of Dharma and Adharma. Both sides had good and bad deeds. If it was a sin to remove a woman's clothes, then it was also a sin to stake his own wife.

Book 18 chapter 3

12 शुभानाम अशुभानां च दवौ राशीपुरुषर्षभ यः पूर्वं सुकृतं भुङ्क्ते पश्चान निरयम एति सः पूर्वं नरकभाग्यस तु पश्चात सवगम उपैति सः

13 भूयिष्ठं पापकर्मा यः स पूर्वं सवर्गम अश्नुते तेन तवम एवं गमितॊ मया शरेयॊ ऽरथिना नृप

Here it is written that the scenes of hell only were deception. Nowhere written about the scenes of heaven and Kauravas being illusion.