b2evolution is a multilingual blog engine. One writer on one blog could do a post in English, then the next in French, then the next in English again, then the next in Farsi. The flag (and the underlying data it represents) allows posts to be sorted and dealt with with the language in mind. If you don't like the locale flag on every post, you can edit the skin you're using to make it not display the flag.

How can I make the flag clickable so users could display posts only written in french or english or Farsi ?