Additional Rules from the Rulebook
You can't trash the Chapel itself since it isn't in you hand when you resolve it. You could trash a different Chapel card if that card were in your hand.
The Secret History of Chapel
In an article on Board Game Geek, Donald X. Vaccarino commented on the development of Chapel:
- This started out "trash any number of cards" and went to the ever-so-slightly weaker "trash up to 4 cards." I tested a version with "trash up to 3 cards." It was horrible. Just, way slower than the current version, like you wouldn't believe. 
Strategy and Notes
Note: Strategy articles are not necessarily based on fact, but on players' experiences or simulation programs. Certain cards will be stronger in some set-ups and weaker in others.