Breakable/alterable artifacts
Kicking, the poison hands corruption and cursed scrolls of repair can affect normally indestructible artifacts.
Problem
Kicking and the poison hands corruption can break and alter the artifact potion of literacy, even though artifacts are indestructible and immutable. Cursed scrolls of repair can break any other artifacts.
How to reproduce it
Potion of literacy: 1) drop the potion on the floor. Move a square away from it. Try to kick the square the potion is on: it'll be shattered and lost. 2) attempt to drink or pick the potion of literacy up with the poison hands corruption, and without thick gauntlets. It'll be turned into a potion of posion.
Any other artifact: read a cursed scroll of repair and select the artifact as the item to "repair". It'll break. Using a non-cursed scroll on the same item will fix it back.
Notes
The potion of literacy "harmlessly bounces off" monsters and doesn't break upon hitting the floor like regular potions do.
The scroll of repair exploit can be used to mass-bless sis this way.