As far as I know, the difficulty must be re-targeted every 2,016 blocks. It is increased or decreased depending on how long it took to process the previous 2,016 blocks.

Block 0 (genesis) has a timestamp of 1231006505, and block 2,015, has 1233061996. That makes a difference of 2055491 seconds, which is roughly 23-24 days. That is more than 2 weeks (14 days) so, the difficulty should have been decreased a little at block 2,016, but it didn't. It remained exactly at 486604799.

It also didn't change at blocks 4,032, 6,048, 8,064, 10,080... and I haven't checked anymore.

What kind of Dark Magic is behind this anomaly?