It is common, especially with those with less experience. To solve this discuss competition. That everyone is growing n their careers and that the best performing and in greatest demand will receive more income.

But, and here is the key, you emphasize the need for team work and harmony among the team. So if an employee talks about their salary and creates disharmony among the team then you have little interest in promoting them again. It is a tough situation if they are your best performer but if they create disharmony for ten then it is not worth having the,

In the US we have had highly skilled and highly paid sport players in basketball and football whose careers were well below what they could be since they were disruptive to a team. The US football player Terrell Owens is a great example of this.

This may be not especially in VN but to me may have at any company around the world. Though revealing individual salary is not recommended, I think each company should have a clear and transparent policy on Salary scale (for example: Manager start from 10mio, experience one varies on top 20%, more than that should move to the next level...) and salary increase (for ex: 10% for total team pool, dividing to each by performance appraisal..).Main reason People chit chit about salary because they think company may treat them unfair, they need to know how "unfair" it is in order to fight for their additional benefits. This is very bad for the company moral...

Good point about ranges - most companies will have job titles assigned to grade levels and will have ranges of salaries for each level. So an "Aq8" may have a $25,000/$28,000/$33,000 range reflecting the low, midpoint and high range. Some companies make this very public and others not. The US government publishes the grades and always includes the grades when advertising the job. Others are more oblique and it is unclear.

I think this is a personal decision, why correct it?
You as an employer need to keep that individually confidential, but the employee is free to give this information.
The taxman cannot reveal the assets of a person, but anybody can boast he has a ferrari and 2 appartments in Q1.
Not a specific trait...