What is a "mylot reputation"?  

You can find all the information here:

: http://www.mylot.com/o/faq/faq11.aspx

You will receive your reputation, also known as a Star when you have a (100) by your name. This will show you how people are rating you depending on the type of discussions that you start here and also as well as the responses you post back in discussions as well. The highest you can get here is a Blue Star, so if you do not get this at first this just gives you a better chance to learn to do better so you can move on up higher in the real as well. Hope this helps.

The star next to your username represents your myLot reputation.
and is based on a scale of 0 to 10 stars with 10 stars being the highest.
When someone rated your comment as a positive one, you'll get a rating.
More ratings will give you a higher reputation here in Mylot.