Is there any intention on preventing or reducing the number of duplicate markets? For example, the same outcome for the same sporting event.
Duplicate markets are possible (even likely for popular events), but the "solution" is largely market driven. Without a compelling reason (below) to compete with other duplicate markets a market creator is wasting time and fees by creating a market nearly identical to one that already exists.
Fees - In general markets with the lowest market creator fees should receive the most volume as users like to minimize their costs
Advertising - A well known market creator that advertises externally may be able to drive traffic to the market he/she creates
First mover advantage - The first market created, all else equal has a good advantage to gain traction before others markets appear and compete for users.
Liquidity - Generally the most liquid markets will receive the most usage and be hard to supplant unless there is a significant improvement in one of the 3 above criteria