What do computer bugs do?

I can set the bug level using the computer from 0-4 for graphical, quest and ultimate. What do these actually do? Are they reversible or am I at risk of destroying my game?

• Graphical: just messes with the graphics of the game, making ASCII art appear and disappear randomly and sporadically the higher the level is.
• Quest: messes with the quests to the point where characters can just fall through the ground or instantly die the higher the level is.
• Ultimate: not sure entirely, but putting it all the way up does give you every item and a lot of health, and prevents you from leaving some quests.

These are reversible: go back to the computer and type "bug x 0", x being whatever bug you have open. Things will go back to normal (for most bugs, anyway).