TLDR
The dark comedy tag probably comes from the irony and discrepancies found in series. The funniest thing in this kdrama are the court officials labeling actions as treasonous and recommending to resolve it with actual treasonous solutions - and all the king does is glare 😂

The show was hinged on the lack of information sharing - a trope less used in kdramas compared to the worn out "misunderstanding" trope. And why da peck do they keep on discussing their secrets just loud enough for eavesdroppers to hear? 😅 😂

This entire series would have been a lot shorter if the mother just told her sons their entire line would be annihilated if someone else becomes the crown prince. Because of the lack of information sharing, they remained petulant, unmotivated, and just overall childish.

The Characters
Old granny who hungers for the "Queen" privileges she never experienced decides it was time for her main character era so she flexes and show who is boss.

The queen consort who tries her hand at being authoritarian after years of permissive/neglectful parenting but gets pushed back by her sons in spite of her efforts to shield them from the realities of palace life.

The grand princes who live a life of the idle rich and couldn't wait to leave the palace. Shielded from the realities of palace life, they remain ignorant of how their lives were already in danger just by misbehaving.

Background
Prince Sado did a lot worse than what the grand princes were portrayed to have done in the series and was not punished for a long time in spite of the atrocities and body count he left behind so I was not expecting the Queen to actively put in effort to rein them in.

Inconsistencies
I am surprised at the corporal punishment shown given how by court rules a royal body could not be defiled - but then again, it is fiction so let's shrug it off.

Considering how the kdrama wanted to portray the queen as having switched to authoritarian/authoritative parenting, it didn't make sense that she was not forthright about what would happen if they did not start behaving. One would expect a mother to be honest to her sons about the possibility of their lives being in mortal danger.

Ultimately, this is a story about women in the background pitting their sons against each other for the sake of status, pride and survival while the men strut about in their robes thinking they were actually the ones in power. A true Confucian masterpiece.