Wha? Isn't the white lettering normal?
Okay, I found it.
holybanana wrote
Somewhat of a spoiler.
I believe you can get any state except polymorphed, life saved or searching as intrinsic due to an unintentional feature. This is because permanence is represented in the game by setting the state counter to 65535 ticks (roughly 32.8 hours). If you can boost your counter over this, when it drops back to 65535, the state is permanent and can only be removed by magical means, for instance eating grey unicorn flesh. I have gotten permanent teleport control in a real game twice by eating a horde of blink dogs.
holybanana wrote
You can get permanent haste from fountains. Also slow. Neither affects the game so much, as the danger system eventually starts to take the state into account when deciding what it is going to throw at you. Of course boss fights are a bit easier/harder.
Permanent invisibility, on the other hand, has big consequences. You can easily escape from many monsters, for instance golems and kaimikaze dwarves. Hit and run tactics become more effective. But you can no more do business in shops and the danger system creates much more dangerous monsters at you to balance the fact that they can't see you. So you not only can, but need to retreat more often. (Of course, only the generation of monsters without infravision or ESP is affected this way.)