I was experimenting with the new commands and when I used "/setblock ~ ~ ~ portal" (Without Quotes), it put a portal block there that I cannot get rid of. It also affects naturally generated portals with obsidian frames and even in creative mode, the player cannot break the blocks. You can only remove the block by having water flow into it.
Update: The problem is that you can no longer break Portal blocks in Creative mode, as you could before in 0.15.7 and earlier. (I am so sorry I forgot to include this new part earlier.)