Denisova, you're looking at an older version of the map. 2.2 I believe. The newest version, 2.3, has that spot labelled as C7, and I believe it's being applied for by Rouran (you could pull post seniority if you wish, but I suggest you talk to him about it). C6 and C5 (the two island-esque spots) are available however.
Can I get C6, then, Khalistan?
At the Dec. 1st update, I can still put you on the C6 islands, but because Rouran has not reached the required number of posts, C7 is technically still available.