I know you said you plan to make this modification for the upcoming release, but my client wants to launch his site early next week and they have over 300 active members who will be notified to go to this site and register.  My client has a list of their active members and will need to activate them, but if only one member is questionable and they cannot use the Activate all button on the Admin CP > Users page, and instead have to activate them individually, they will be in for a lot of work to send individual emails out to all members to notify them that they have been activated and can now visit the site.  

Is there a quick fix that will cause the Activate link on a per user basis under Pending Registrations to send out the email notification auto?

And if you remember a similar thread, the above request is slightly different than this one, although once my client gets the bulk of their currently active members signed up to the site, then having that new release code in place to send auto emails upon creating a new user will be very helpful and was asked about in my training session today with them.

Of course the easiest way to accomplish it is to first delete the one suspicious one, and then activate the rest in bulk, as clicking on them individually will also take its time. (To do individual actions faster, just click "delete" or "activate" links to open in new tabs on the background, and click away through the whole lot of them at once.)

However, whether you click "Activate User" individually, or click "Approve All", "your account has been approved" e-mails should get sent out to everyone who gets activated. Does this not happen? Or did I miss something in the above?

Sorry about that one.  I could have sworn that this was discussed and I was told that only when Activate All is selected that the email goes out, but I must have put by brain on up-side-down that day.  I checked and indeed when I activated an indiv., the email went out.  

Excellent! I thought my brain was upside down as I was reading the code...