Izumi Konata and Suzumiya Haruhi share a bond on and off the anime shows. Although it is unknown to me how anyone ever created Kurokona, I'm gonna make a random guess that The Disappearance Of Suzumiya Haruhi had a hand in it.
Kurokona is often seen depressed or apprehensive and often wears glasses. Probably when the news got out that Haruhi was gone she secluded herself, died her hair, grew a darker outlook on life.
It's possible that Haruhi herself even had a hand in changing her persona so much.
Aside from the obvious glasses and hair color, slightly worth mention is the average hair length has decreased. Whereas her norm would be from hip to calf hair length her now black hair is consistently shorter.
To make an even broader guess; Her change made Konata grow a larger consciousness of her surroundings and with ehr depression she grew more mature. She then abandoned manga, anime, and video games to further her studies and increase relations with her friends and family. Her glasses are proof that she has lost something, namely her eyesight, possibly from her long addiction to late-night gaming/anime, and getting them is proof she has given into her addiction being bad for her health.
Of course she could just be the fan-inspired counterpart to follow after Kyonko as people would rather see a calm and conformed Konata than a male one.
