Which of the following is a best practice regarding Expressions in Appian?

In Appian, the best practice involves focusing on deployment compatibility, which is why avoiding keyword syntax can be beneficial. Keyword syntax, while it can be more readable, may lead to issues when dealing with expressions across different environments or versions of Appian. Ensuring that an application remains compatible across these variations is critical for seamless deployment and function. Therefore, steering clear of using keyword syntax helps maintain consistency and compatibility, ensuring that all expressions will work as expected regardless of the environment.

The other options, while they may have their merits, do not align with this fundamental principle of ensuring compatibility during deployment, which is a crucial concern for developers in Appian.