There are managers, and HR people, who break into ire when they discover that an employee has updated her resume on a job site. In the midst of their disapproval they might also consider that that employee has been uncommonly foolish.
And then there are HR people who expect this and see it, and decide not to remark on it. Who might take it as a sign and ponder how to deal with it without accusing the employee of wrongdoing. There are managers who react to the employee's hint of looking at better prospects with the assurance that the employee is valuable, and an offer of help in exploring career opportunities outside the company.
I realize that the second is far more rare than the first. Yet isn't the second approach far more effective?
If you were in the second situation, would you have second thoughts about leaving? Would you be more inclined to stay, or come back later if circumstances permit, than you would if you were in the first situation?