BuddyPress.org

To a certain extent I’d say the answer is yes it’s possible, all the read only pages at least. Take a look at the overload files in plugins/buddypress/bp-teplates/bp-legacy/buddypress/members/single. These are the page components that make up much of the bp profile pages.

Any emails sent via BuddyPress like new messages from users etc

There’s different ways of solving it, you can look to this old post for some pointers.

or you could do something like this

<?php
function opengraph_tags() {
    // defaults
    $title = get_bloginfo('title');
    $excerpt = get_bloginfo('description');

    if( bp_current_component() ) {
        global $post;
        setup_postdata( $post);
        $title = get_the_title();
        $excerpt = get_the_excerpt();
        if ($excerpt) {
            $excerpt = strip_tags($excerpt);
            $excerpt = str_replace("", "'", $excerpt);
        }
    } ?>
        
    <meta name="description" content="<?php echo $excerpt; ?>"/> <!-- general meta tag -->
    <meta property="og:title" content="<?php echo $title; ?>"/> <!-- facebook meta tag -->
    <meta property="og:description" content="<?php echo $excerpt; ?>"/> <!-- facebook meta tag -->
    <meta name="twitter:title" content="<?php echo $title; ?>"> <!-- twitter meta tag -->
    <meta name="twitter:description" content="<?php echo $excerpt; ?>"> <!-- twitter meta tag -->

<?php }
add_action('wp_head', 'opengraph_tags', 5);

You’d then be able to write the description of the buddypress page in the excerpt input while editing whatever Buddypress page. This only solves the main pages though.

If you’d like to go further for group, member and activity SEO you’d have to follow it up with some more code.

Presumably this is referring to the BuddyPress Group Email Subscription plugin? Have you tried rasing this as a feature request on that plugins forums?

I think there’s a few ways of achieving this, for one thing there’s a bunch of plugins that change the default activity feed in the members howmepage. Take a look at https://buddydev.com/plugins/facebook-like-user-activity-stream-for-buddypress/ That would make a good start.

Another way is to Overload the activity-loop page in BuuddyPress, this basciall does what the plugins do, but without a plugin. You can take the default page from the plugins/buddypress/bp-templates/bp-legacy/buddypress/activity/activity-loop.php and change the way the activity filters work for your site. It’s a bit more advanced but there’s plenty of forum posts about doing it.