BuddyPress.org

Hello All.
I’m trying to setup a site that uses buddyPress, and I have an issue that I hope somebody know how to solve.
Currently the settings for​ private groups looks like this:

This is a private ​group

• Only users who request membership and are accepted can join the group.
• This tribute will be listed in the tribute directory and in search results.
• Group content and activity will only be visible to members of the group.

I need to the third item to change to this:

• Group content and activity will be visible to everyone but only group members can post comments.

How do I make this happen?​ Is their a plug in or a place in the code to change such a thing?​

Just in case, what i need is not only a matter to change the text, but the function that make to happens what the text says.

Thanks a lot!