A Solidity developer is someone who specializes in programming using the Solidity language, which is primarily used for developing smart contracts on the Ethereum blockchain. As for the 15 features/advantages of a Solidity developer, here are some:

1. Expertise in Solidity programming language.

2. Ability to write secure and efficient smart contracts.

3. Understanding of blockchain technology and Ethereum ecosystem.

4. Knowledge of decentralized application (DApp) development.

5. Proficiency in using Ethereum development tools and frameworks.

6. Familiarity with Ethereum Virtual Machine (EVM) and bytecode.

7. Experience in testing and debugging smart contracts.

8. Understanding of token standards like ERC-20 and ERC-721.

9. Ability to integrate smart contracts with front-end applications.

10. Knowledge of best practices for smart contract development.

11. Awareness of security vulnerabilities and how to mitigate them.

12. Proficiency in using development frameworks like Truffle or Hardhat.

13. Ability to interact with Ethereum nodes and APIs.

14. Understanding of gas optimization techniques.

15. Continuous learning and keeping up with the latest developments in the Ethereum ecosystem.