Idempotent methods are important; I'll give you that. However, the struggle between ACID and CAP theorems would suggest these are just words we will try to live by. I rather dislike having to imagine what it means for my DELETE operation to be bouncing around the network for a minute.

  > unless the server intends to complete the operation

A gerund; it intends to, without any guarantee of recency, to perform the operation. The very same problem that required the operation to be idempotent; it can't be guaranteed the operation is already done, only that it intends to complete in time. A 200 will only describe the status and does not require the description to be "deleted."