I think the best way would be to sort them in the release order. Much less work for you with all the editing and mowing around the girls.

Personally I would do a new comment for each batch of promoted girls, that would be very easy to navigate through, since each comment would have exactly 3 girls in the order they were released.
Sure once you get to a hundred sorting them by whatever might be better, but in that case I would change the OP to a list, no skills nothing. Just a list of the names, the actual skill would be in each of the comments with the girl.
The thread is mostly for quick reference, so making it streamlined and easy to navigate through is the point. People can look up the girl, and for more details then go to the Wiki, but at least they have a good idea which girl they are looking for thanks to the thread.