They can probably hear and just deliberately choose to not mind or talk abt it. You know with those kind of job u should see nothing and hear nothing.
Really early on jae-shin mentions how no one will be able to hear Lee nok if he calls out for help. So there’s deffo some of his powers involved
He sends all his servants away when Jae-shin comes to him.
He has protective magic around to soundproof the rooms lmao he mentioned it awhile back
this man is a whole future king to an entire nation and no servant or guard or nothing hears him getting his cheeks beat every night I’ve seen historical kdramas and they always have servants or guards two feet away from them but like no one hears nothing