Majority of top comments trying to justify or excuse a younger sister’s sexual attraction to her older brother. All trying to make her a victim, when the older brother (OP of the thread) is clearly traumatized by her ‘confession’

Haven’t clicked but already know which post you’re talking about. This top comment was a big Reddit moment:

Good start, older brother. There's a lot of sickos and creeps out there that take advantage of family. But, you can do better for her. I'll explain. Chances are, she respects you. You're a guy, who shows her respect, love, and treats her sweetly. You get along. You have each other's back. It sounds wierd, but barring sex, she probably looks at you as the model for what she wants in a boyfriend. At her age, it's understandable to a certain degree that she would have some wierd feelings and thoughts. Acting on it and telling you is the line. Now, you have responsibility here too. You can't be her supportive great older brother that kicks her out for good and shows her the cold shoulder. You need to continue being the brother she admires, and stay there. Nothing more. Don't betray her confidence, that may drive you apart. I'd sit down with her, and talk about it earnestly. Tell her that her friendship is important, but you don't think of her like that, because she's your sister. Tell her you'll still always be her brother, and you don't want things to change, but you will not ever be someone to consider for sexual partners. She's feeling vulnerable, and isolation will cause more of that. She needs support too, and gentle but firm correction. If she wants to talk about men, tell her it's okay to take the traits she likes in you, and try to find them in a man. Every girl needs a baseline, a role model, so she can have someone to compare. Remind her it's okay to be a virgin, it'll pass someday, but she should be patient and wait for the right man. And it isn't you.