BuddyPress.org

I assume you’re specifically talking about customizing a BuddyPress template. If so, then you need to look in the BuddyPress profiles tables in MySQL.

For instance, the field definition for the “Full Name” field is stored in the wp_bp_xprofile_fields table and any corresponding datum is stored in the wp_bp_xprofile_data table.

With respect to this:

At the moment Buddypress/WP MU makes it very hard, perhaps impossible, to flexibly use member’s real names or other data (companyname, city) in the site or have something like ‘Hello John’ in email notifications.

That is not true. Any piece of stored data can be accessed and spit out in any number of ways. It just must first be in the database. Look in the bp-xprofile.php file and the bp-xprofile subdirectory for a number of functions that can be called to extract a user’s data.

By the way, I did see your other post about this topic and it was answered appropriately. With the default WPMU and BuddyPress setup, you will not be able to use a user’s full name until they’ve entered that data. They will not be able to enter their full name until after they register.

So, unless you hack the wp-signup.php or register.php files, and require that a full name be provided when registering, you will not be able to send them a welcome email with their full name since that piece of data does not yet exist.

All of what you are asking is possible but requires either a pre-existing plugin, a custom hack, or your ability in customizing and coding a BuddyPress template.