mitsuruga wrote:
Why can´t I post in the Feedback Thread in the Sale Section? It is locked to me. I´m wondering because I could in the past. Help

This one? Yeah, it's been locked for over seven years now, when we changed to using the new feedback system. It looks like the post explaining the new system has been removed for whatever reason.
Short version: You give feedback directly to users now. Click on the line of feedback numbers that you see under a user's avatar (when looking at their post) or in the Profile section when looking at their user profile. Click Add feedback, select whether you were buyer or seller, or if this was a trade, select negative/neutral/positive (positive is default), add thread ID and additional comments if you want, and you're done.