Parmandur
Book-Friend, he/him
Out of curiosity, how do you get that interpretation at the end? I ask this not having access to my rulebooks right now, so I might be off ...
But if the magic item raises your natural ability to 19, why would you be able to use an ASI to get to 20? Wouldn't the ASI just raise your (base) natural ability, which, when you wear the item, increases to 19?
Yup, ASI wouldn't help, unless the score was already 19.