#1 - Feb. 26, 2013, 1:24 p.m.
The description of this update was pretty unclear, so let me clarify. The change to portal made it so that you can’t interact with a portal that is on the other side of a wall from you, but that a portal whose entrance and exit are on opposite sides of a wall will still function.

Used to be you could put both inside and then jump in from the outside without having to create a portal on the outside.