Has this planet always spun around or is it something new?

Big who cares!

It's always spun. A lot of the other ones do too.

[duplicate post removed -Phaser]

The 3D planets only show up if you have the upper levels of background detail. But, for those cases, they have been 3D and spinning since alpha. For users who started out with the "cooked down" texture-only backgrounds and are now seeing them with full detail, you may be noticing the spinning planets for the first time.

Some of the rotations are so subtle you have to zoom in to see it.

Ah, I just realized that it was once I bumped up the graphics that I started noticing planets. Unfortunately with my low end laptop this resulted in some weird ass lag and more explosions of me during PvP action. Guess it's back to shit graphics.