I understand by your fatwa no. 87404 that sleeping naked is permissible in Islam as long as no one would see me, but is it permissible to be nude when alone and ensuring that no one would see me? By that, I mean taking off your clothes when alone and doing everything naked for the comfort of it? Is it haram?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger. 

According to Muslim scholars, it is disliked to be naked when it is unnecessary to do so because this contradicts being bashful; verily, bashfulness brings nothing but good. They relied on the hadeeth narrated on the authority of Muʻaawiyah ibn Haydah that he asked the Prophet, sallallaahu ʻalayhi wa sallam, “O Messenger of Allaah, with regard to our ʻawrah (parts of the body that must be covered in Islam), what may we uncover of it and what must we conceal?” He, sallallaahu ʻalayhi wa sallam, replied, "Cover your ʻawrah except from your wife and whomever your right hand possesses." Muʻaawiyah said, "O Messenger of Allaah, what if there are many people mixing?" He said, “If you can, do not let anyone see it.” Mu'aawiyah said, “O Messenger of Allaah, what if one of us is alone?” He said, “Allaah has more right that we be shy of Him than of people.” [Abu Daawood, Ibn Maajah and At-Tirmithi]

Al-Munaawi commented on the hadeeth as follows:

“The hadeeth asserted that Allaah is worthier of the person's bashfulness than people; this means that Allaah is more deserving than people that one should be modest and bashful of Him, i.e. concealing one's ʻawrah even if alone. Verily, nothing can be concealed from Allaah, The Exalted; He sees all that is hidden and seen alike; however, the Muslim should be bashful of his Lord out of the becoming etiquette of the Muslim entailing him to conceal his ʻawrah and dress modestly (even if alone). Al-ʻAlaai' and others advised that this is a reference to the muraaqabah (mindfulness of Allaah), one of the highest stations of spiritual awareness. When the slave is mindful of people, he conceals his ʻawrah before them out of bashfulness and modesty; rather, he should be more bashful of Allaah, Who sees him in all times and all states for a greater reason. There are many reasons for being mindful of Allaah, the most significant of which is the due bashfulness of Him. It was said that Ibraaheem ibn Adham once performed prayer while sitting down and then stretched out his legs (towards the Qiblah); he heard a voice saying, 'Is this how you sit before Kings?' Thereafter, he never stretched out his legs (towards the Qiblah). A wise man once said, 'When a slave stays naked while being alone, it is an indication of his lack of the due mindfulness of Allaah; does he not know with certainty that Allaah watches him?' Abu Bakr would cover his head when answering the call of nature (entering the toilet) because he would remember that Allaah is watching him. ʻUthmaan used to take his baths in a dark room so as not to see his own private parts...” [Faydh Al-Qadeer]

Allaah knows best.