I think it was explained in the previous thread:

First off - "Than" is used as a comparative statement - comparing this to that. (example: I am older than you!) "Then" usually refers to a time or sequence (example: "Then" we went to the store.)
I know I am a horrible offender of this rule. I think it is because it is difficult to determine which is which when spoken, therefore it is not as obvious to me when writing. As a default I tend to always use then, and I'm sure it is often incorrect.