It's considered informal, and in some dialects (mine included) unusual. The Grammarly link you edited into your first comment doesn't even support a classification of "learnt" as informal, it literally just describes it as a dialect difference. You're doing the same thing as telling a Brit that they're spelling the word incorrectly if they write "colour"
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
replies: