I'm kind of back and forth on this, I also don't like people removing the whole post to say "Sold".
First topic, it seems better to have the mod be able to close the thread because what if the buyer has some questions, and doesn't want to start a new thread that would look like negative feedback.
As for the SOLD part, I like to compare prices between parts, and if someone replaces everything with SOLD, hard to see what they were selling and how much, you can only see the subject and guess from there.