BuddyPress.org

It’s fairly easy to get the comment count for a particular user.

$args = array(
    'user_id' => bp_loggedin_user_id(),
    'count'   => true
);
$count = get_comments( $args );

From that point on, depending on what action the user is taking on your site, you can check the count against a pre-determined figure:

if ( $count < 10 ) {
    // The comment count for the logged in user is less than 10.
} else {
    // The comment count for the logged in user is 10 or more.
}

It isn’t really a copy-and-paste example. You’ll need to be comfortable with PHP and WordPress 🙁

Alternatively though, you could look for a plugin in the Plugin Directory. Maybe the functionality you need already exists?