Idk why this q reminds me of this: https://m.youtube.com/shorts/EamFJ6KGYeg
I feel like if it's consistent, it's an artistic choice. The artist probably loves to add this characteritics to make the drawing more 'human' instead of having perfectly symmetrical features. As for having a meaning behind it, I'm not sure. Unless it's devicive to the story and was mentioned, I guess that's the only way the reader would know. :)

ive noticed this recurring trait that shows up mainly in the manhwas i read, there’s sometimes a character that has asymmetric eyes (one monolid, one double eyelid). i can tell it’s a conscious decision on the artist’s side, since they always remember to draw it even for chibis (eg., alpha trauma, sparkling baby, i’m not your guide to destiny, banana scandal, can you operate on love?, just to name a few) but i always wondered is there supposed to be some sort of meaning behind it? is there a trait that tends to be associated with having one double eyelid?