From Marvel's website:
So even Marvel know's there were vast changes made to the character from when she was introduced as a blonde British lady to becoming an Asian spy.
If we're just going to throw random facepalms at people, then please, allow me to give your rebuttal a few of these:
In the section you quote, the "new powers" include:
1) a temporary ability to be undetectable to machines, which happened in #227 before she entered the Siege Perilous, and ended when she entered it, so that is moot
2) teleportation powers from The Crimson Dawn, which didn't even first appear until #330
3) and powers she gained by swapping abilities with Jean Grey, which has nothing to do with going through the Siege Perilous and again happened much later
So do all the issues where she gains these three other sets of powers also represent the debuts of entirely new characters?
The only supposed "new power" she gained with #256 was the psychic knife -- which wasn't a new power at all, but simply a focused manifestation of her telepathy/mental bolts, which she could already do.
The fact that she looked Asian and had a new costume, I mean, so what? Just because the graphic redesign was successful in making the character more popular does not make it her first appearance.
The psychic knife is her trademark look/weapon. It's as important to the Psylocke's character as Wolverine's Claws are to his character.
Just so were clear - a new role defining power, a change in her ethnicity, a new costume AND changing her profession from model to assassin isn't a new character?
What's a character have to do around here to get the 1st appearance notification? Just get a Bejeweled gem in his forehead and change his name? Is that all?
I call BS on that.