I think the main danger is when truth and improvement is compromised in favor of niceness. Sometimes you are wrong, and that's definitely not a comfortable position to be in. It's not going to feel good to have it pointed out. And yet it's imperative that it is communicated. Wise individuals should not attribute the discomfort to the person pointing things out, but to mistakes themselves of course.
There are cases where marking errors is done to belittle, offend, portray incompetence, etc.; however it shouldn't be too hard to avoid those perils -- it's just a matter of showing how mistakes are (mostly, and to a measure) inevitable, not disqualify the person for the mistake (i.e. recognize it's something that is not inherent and can be fixed). Avoid broadcasting mishaps (communicate one-to-one), be supportive when pointing things out, and the environment is going to be better for everyone.
Superficial niceness might be worse than sincere harshness indeed. But the best is bold sincerity and support, which ultimately creates trust and robust, enduring relations.
There are cases where marking errors is done to belittle, offend, portray incompetence, etc.; however it shouldn't be too hard to avoid those perils -- it's just a matter of showing how mistakes are (mostly, and to a measure) inevitable, not disqualify the person for the mistake (i.e. recognize it's something that is not inherent and can be fixed). Avoid broadcasting mishaps (communicate one-to-one), be supportive when pointing things out, and the environment is going to be better for everyone.
Superficial niceness might be worse than sincere harshness indeed. But the best is bold sincerity and support, which ultimately creates trust and robust, enduring relations.