Question about the Mormon concept of “the atonement”?

I appealed a ban from a Mormon subreddit and in their reply they wrote “In the atonement, a person who has repented is as pure as someone who hasn’t committed sin.”In my Christian background, atonement simply means asking for God’s forgiveness and repenting. I tried regurgitating the advice that the Mormon mods gave me to a pleasant and kind woman I met on the 90-day-fiancée sub here:https://www.reddit.com/r/90dayfianceuncensored/comments/jm036v/question_about_down_voting_posts_about_the_big/gauoeyq/?utm_source=share&utm_medium=ios_app&utm_name=iossmfI’m left feeling unsure if the LDS concept of atonement differs from the mainstream Christian/Protestant concept of atonement?Thank you for reading. 🙏