These are, in fact, specifically listed as how not to write a resignation letter. But as burning-your-bridges letters go, you could do worse than:

I’m resigning. The voices have told me to. It was also the voices that told me to bury the photocopier and shave the accountant. However, the graffiti and general vandalism in the stationery cupboard was all my own idea - I don’t like being left out.

So perhaps we shouldn’t use them. But oh, we can dream of using them.