Hmmmm. Does this work in the rules?

• "player"+"target": Yeah, I'm pretty sure this stops you casting Inspiration targeting yourself.
• "permanent"+"target": Does this stop an Icatian Lieutenant targeting itself? Is it the creature or the player who targets?
• "permanent"+"damage": Yeah, this definitely works to keep Crypt Rats or Skirk Fire Marshal safe from themselves.
• "player"+"damage": This I think will be the one that confuses the most people. It doesn't stop my Earthquake damaging me, because it's not me that's dealing the damage - it's Earthquake. Many people write custom cards as "Deal 3 damage to each player", but proper templating is always "CARDNAME deals 3 damage to each player".

Given this is you who created this, though, amuseum, I'm guessing perhaps you intend this to come with a Comp Rules tweak to say that any time an object a player controls deals damage, that's also considered to be the player dealing damage? By analogy with 702.16j on "protection from a player" a la True-Name Nemesis, it'd make sense.

Maybe it could be templated as TNN:

Enchanted permanent or player has protection from itself.

Since objects already can't block themselves and being attached to themselves is... I forgot whether really niche and hard to recreate or outright impossible... Since that's the case protection will cleanly take care of this...

I don't know whether the rules already cover protection from a particular permanent over e. g. any permanent with the same name, but that's an easy addition to the rules if it's not in there yet.