The Poet trait is making a triumphant debut in Crusader Kings 3, after being left behind in Crusader Kings 2. The new trait is to be added as part of the 1.3 free patch, and will allow players to use their silver tongue to charm, insult, and even torture those unfortunate enough to cross their path.
This new Poet trait however, isn't exactly the same as the trait from Crusader Kings 2. This new version comes with reworked stats, a character interaction, and even randomised poetry, which should prove for some unusual poems. The system Paradox has introduced creates a poem based on one-of-five topics, and then uses a localisation function to generate some randomised lines. The system should allow poems to be "dropped into any event or event chain fairly easily," and will mean that bad poetry can be auto-generated in the future, as the blog post states.
As for the uses of poetry in the game, you can look to torture victims with your god-awful verses, charm other characters, or even use it for diplomacy should you like. Since poetry isn't exactly everyone's cup of tea, this can all go very wrong, so you should be wary before you start spitting couplets.
Also noted in the blog post was a series of balance changes and bug fixes. You can check all of that out over here.