Coping vs. Mitering Crown Molding

I have always coped inside corners in crown molding. It's the way I was taught, and it's the way the books say, and it's the way it's been done in all the old houses I've worked on. However, after all these years, I'm still not sure why it's better to make a coped joint instead of a simple miter. Would someone care to enlighten me?
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It isn't. Coping just makes making a good joint "easier" on walls not square and/or plumb. -----
- gpsman
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wrote:

When the building shifts, when the room changes shape, when the wood expands/shrinks, the corner seem may open up. When coped in the proper direction (when viewed from the entrance door), the gap is made much less visible than if the joint were mitered.
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