The user most likely hasn’t logged in yet. You will find once a user has logged in for the first time, they will become active and show up in the members directory.
You could deactivate BuddyPress and leave the tables in the database without any problems. If you do choose to remove the tables, take a look at the BuddyPress Database Diagram which might be helpful.
In that case, try looking through your theme’s templates. Make sure you’re not outputting the data twice. Also check the filter and action hooks you have set up to be sure nothing is outputting twice.
Notification links sometimes point directly to single activity items. If the activity item is deleted, you’ll get a 404 after clicking the notification. Could that be happening?
I think the JavaScript will detect a new option list value and kick off a new query to load the new info. I’d imagine you’d need to write the JavaScript listener and the new query yourself but there may be a way of hooking in that I’m not familiar with. Perhaps someone else here can comment?
Just an idea: if you have no success finding a shared BuddyPress calendar, try searching for shared WordPress calendar. In BuddyPress, members are actually WordPress users so in theory things should work. You’ll need to test though, as always.
