Re: How to remove those brackets ?
Actually the code you’re looking for is to be found, for example, if you look in groups/index.php at around line 17 & 20 you’ll see:
printf( __( 'All Groups (%s)', 'buddypress' ), bp_get_total_group_count() )
You could simply remove those parenthesis from around the %s. Of course you would want to do this from a copy of the file as used in a child theme.