In questions like here - In Ethereum, what is an uncle block? - people are saying that uncles are just being included in some of the next 7 blocks. So far so good.
What if a uncle is conflicting with the corresponding sibling block?
- Is it discarded?
- Can this concept being misused to attack the consensus?
- How often does these conflicts occur?
To me the chance of having conflicts in two sibling blocks seems fairly reasonable, since both miners tend to choose the transactions with the most payout.