Lizardly slurping up some high-protein bugs:
Refunding skills resets your lizard skills but doesn't recover the points you spent on getting lizard skill points, so not only is the exchange one-way only, but you also lose all of them if you scrub your mind clean.
Also, I think I got the NORMAL ending despite loading a savegame that should have reset me to a point before having talked to one of the two specific characters who might have been necessary for that ending, so in short, I think an older save file retained variable states from after that save file was made.