What do those little stars by some users names mean?

These stars are representing your rank. Ranks are a way to measure your participation and the quality of your discussions and responses. These appear only once you cross 100 responses margin. Just like now, you have reached 100 so you can see your star which you say is a 5 which is not bad. It will increase with time and it helps in your earnings a bit too. The highest star's 10 which shows that you spend loads of time on mylot and give quality responses and discussions.

Hope this helped you clear the concept of the stars. If you still have questions then you read your alert columns as mylot as comprehensiely explained it there.

Cheers!

I see you have progressed to a 9 star yourself - Well done. I think I am still an 8 but I am very trying!