Sometimes, getting to the logic of to make a rule to act the way you want is the hardest part. Here's a thought for you - How many of these "Re: " messages are from people you know? Probably none. Therefore these 2 rules should catch a fair amount of these messages:
[ol][li]For messages from someone in my address book, stop processing more rules[/li]
[li]For all messages, move them to some 'possible junk' folder[/li][/ol]
If you have other rules, these would need to be near the bottom of the list because mail rules are processed in the order listed. The logic is that if the person is in your address book, it's probably a real reply, so don't do anything else. Only if this rule doesn't apply, does it continue on to the following one, which is a move but could be a delete when you are comfortable with it working properly. There are still some potential problems with this though: If it is a valid reply, but the sender is not in your address book, the message will be moved when you don't want it to. So, contining this line of thinking, if someone that's not in your address book is replying to a message that you sent, there's a high probability that your e-mail address is somewhere in the body of the message. Therefore, the above rules could be modified as:
[ol][li]For messages from someone in my address book, stop processing more rules[/li]
[li]For all messages, move them to some 'possible junk' folder, except if my address is in the body[/li][/ol]
There is still a small chance of catching a message that you don't intend, but this should get most. If you have other rules, you may be able to work this concept into what you already have.