We distinguish between 'an interest in nothingness' and 'an interest in nothing at all'. The latter feels no call at all - neither from existence nor from the non-existent, not from the visible or the invisible. No internal or external pull (or push) moves him. This is a disinterested apathetic person moving through life in a state which could be written off (by some) as anhedonia.
The other - i.e., the ones interested in nothingness - do not suffer the lack of the 'pull'. Their object of attraction, however, is the transcendental - formless, attribute-less, timeless, and even witless. This pull is a way in which the search for the absolute truth expresses itself in our heads. It generates an obsession with निर्गुण, निराकार, and निर्विकार. Why (and how) does one develop a taste for such unmentionables could be fertile field of inquiry, but I'll dare not foray lest bitter realizations arise to haunt me! But such tendencies sure have larger consequences in important areas of one's life. Moving further, I'll use 'he/him' to refer to the being who has acquired the flavor for nothingness.
He bears a nonplussed existence in social spaces and fails to assimilate himself with the mores. The hierarchies, the rewards, the penalties, and the climbing of the social ladder make little sense to him. He remains unconvinced, yet has to dance the social dance. The constant performance is a reminder of Mr. Meeseeks': 'Existence is pain'. The uninitiated could read him as suicidal. Nothing can be farther from the truth! The need for constant performance and the requirement of succumbing to needless social requisites just suck the fun out of life. It is the dejection of a person who realizes the beauty of life, but is forced to waste it in unworthy mindless pursuits.
His sense of self is persistently under question. The comparative detachment from (and a limited interest in) worldly affairs provides ground for relatively deeper introspection. Finding 'meaning' in things, events, actions guides him to act willingly. The lack of a sense of meaning steals all joy. The sense of self is not build brick by brick (or characteristic by characteristic). Here, you'll find a being trying to identify the inner being through the नेति-नेति method. Naturally, only Shiva grants him peace; Krishna remains an enigma he cannot grasp! शिवोऽहम् : the ultimate goal!
For him, the idea of self is only ever deconstructed. The self often forgets its bodily limits, and attempts to embrace more than itself. 'Love' is the final word. It is a confession that he has found oneness with another: rather lost the sense that the other is an 'other'. It dissolves the 'ego' and expands his soul. The unwavering soul, lost in search of the formless, wishes formlessness for itself. Intuitional submission is the only love it knows.
What about an interest in nothing at all? That could be a topic for some other time. But you, who read this blabbering to its end, sure aren't one of them!