When characters change gender using magic, alien science, or other metaphysical means for an extremely extended period of time, but only when there is a sexual encounter with another character during that time period.
When characters change gender using magic, alien science, or other metaphysical means back and forth from male to female, but only when there is a sexual encounter with another character.
The difference between them seems to be duration; the stipulation of sexual activity is, to me, questionable, especially since both of the characters that the terms come from were minors (at least in appearance).
It did remind me that I hadn't listed Ozma of Oz in the 'interests' section. This is an understandable oversight, as I've never read the Oz books myself, but someone had mentioned it before and I'd intended to include it earlier. This has now been taken care of.
As fans of the series know, Abstract Gender is now into it's main story arc. As an major plot point, Brian/Brittany can transform between the two states at will, which for the time being at least, Ryan/Rachel cannot. It will be interesting to see how this plays out in the series. Meanwhile, the 'transgendered birthday party' in El Goonish Shive has finally begun, with the very reluctant Justin being the first to get altered. We can expect quite a bit of character development over the next twelve hours of story time (which will probably go for a year or two real time :)); already, there has been a very tantalizing flashback for Justin as he was getting ready to be transformed. We shall see. I find it somewhat gratifying that both series have made at least some passing reference to characters having trouble in their altered forms, though it does not seem to be a major story point in either case so far.