Created by Mass Ascendance. Still a fun concept, though not something I'm expecting Wizards to do this decade.

I am always intrigued by the idea. This one seems simple enough.

Should use its name ("~") in the abilities.

I'm not sure about that. Remember that this token isn't the primary card; Mass Ascendance is the primary card, which defines this card's text. And Mass Ascendance reads much more cleanly if the abilities say "This token", I think. See Awakening Zone, Brood Keeper, Deathpact Angel, Mitotic Slime, Skeletonize and so on.

Well, none of those create named tokens. Sparkspitter does.

Alternatively you could follow the example of Goblin Kaboomist, but then you would still refer to the object by its card type not by its (noncopiable) state as a token, so if you don't use "~", then at least use "This planeswalker".

Yeah, fair enough. I agree Sparkspitter looks like precedent for using the token's name, or alternatively "This planeswalker" would also be better.