am i missing something? why did gojo thank the author for the compliment? when did they find out that gojo was the one who made the outfit
Sorry if you already got an answer, I'm too lazy to check every single comment.
But imagine you're entering an art competition, and you were looking at your own painting being displayed. Someone came and stood next to you then said it's pretty. Even though the person didn't directly say it to you, you would still feel happy when they complimented your work that you might thank the person. (Then the person might ask, "oh this was your work?")
In this case, getting the attention of the author was part of Wakana's goal. During the preparation, they had a conversation about beating the god. Wakana thought the author was like a god, and he wanted his work to be acknowledged.
That's why Wakana unconsciously thanked the author because he was so happy.