I think the employee-boss relationship is a factor as well. Generally speaking, superiors should be able to make constructive criticisms to their subordinates without it impacting morale in a negative manner. That makes criticism a two way street.

Bosses must make sure that they're not all critic with no praise. No one wants to be critiqued all the time without kudos for the good portions and hard work. Tone, body languages, and timing all play into how an effective leader communicates positively or negatively to a team member.

On the flip side, staff need to be able to separate their personal worth from the work that they do. This can be especially tough in some fields and with some personality types such as art, design, and programming. When your work is highly subjective, when you're starting your career, or when their are a million methods to achieve the same goal (with some methods being better without obvious reason as to why), it can feel like critiques are attacking the person instead improving the work.

An anecdote from my personal life: I worked as a paralegal for a while. I started off mediocre at the job, but after a management change, my new boss had manuals that gave standardized instructions on how to do nearly everything. That's when I started to excel. There were many specific times when I would give my boss documents, but he never let them slide. Ever. He would say, "The language and structure of this document is perfect, but you know I can't let anything slide without having something to change." He'd mark something subjective such as substituting a synonym with the same meaning and tone or moving a sentence that didn't affect the language of the paragraph. It never bothered me, but I can see how that would definitely grate on others. In spite of this, he was always full of praise with nothing but positive remarks.

One-word redline => 10 minutes of billable hours.

::Shakes fist:: lawyers! ;-)

Because of the line of work, we were contracted with up front costs. We didn't have billable hours, but hot damn - those little corrections would have added up quickly.

The trick is to frame it as a question, so the original creator "solves" the problem on their own and thinks it's their idea. E.g. Instead of saying "make this blue darker", you ask "this might be hard to read on a lighter background. What can we do to fix that?"

Or even better: "I find this hard to read on a light background, what do you think?". By saying "what can we do to fix that?" implies you want it changed and are not giving the person a chance to explain their decision (if there was one). They could say "I thought the same, but then we tested it with 10 people and everyone found current version easiest to read".

Maybe the key is to effectively manage your team's morale such that they're not derailed by constructive feedback.

I think the point is that sometimes it's not constructive feedback. Sometimes you'd personally just prefer things to be slightly different. But that doesn't mean that the path your subordinate chose isn't just as good as your preference. In those cases, you should keep your feedback to yourself because it's not actually constructive, and in the worst case it actually undermines their confidence.

If you don't have good reasons for your feedback (beyond personal preference), then absolutely keep your opinions to yourself. But don't blindly rubber stamp work product in order to preserve feelings. There's a third way, which this article completely ignores.