Make the resolved button more prominent. I mean I have to really dig to find it. I suggest it is placed in the Thread Tools menu. Or even more in line with edits. For example, if my thread is resolved, I'm generally going to reply thanking whoever for help. On any reply I do on a thread I created should be a check box that says 'Mark as Resolved'. More people would mark threads as resolved if they see it. Sticky reminder posts don't help.