It's why Portal is full of spaces that don't accept portals. A tool that's too useful can bypass the game's challenge.

Except that is justified in world. Only things made of moon rocks (or painted with crushed up bits) can get portals.

Wonder if these things have a ruleset for where they can be placed, etc.

or if Bungie just straight up arbitrarily paints what surfaces are 'allowed' and surfaces just default to no ice platforms.