[KuraFire]

Do we need to put a comma back in the line above it or anything?

Nope, thanks for pointing that out!
The comma's between usernames are added with the implode() function that I call at the end of the hack part. You should not have any comma's (string-comma's, not code-related ones) in your code anymore....

Also, if a staff member is online and invisible, will the staff tag still show up on the line and be blank or will it not show up to regular members? If I am the only staff member online and in Ghost mode, I really don't want the Staff: to show up, if possible. That would pretty well give it away that there is a staff member online but invisible.

I do believe that it won't appear unless there is at least 1 VISIBLE member in that section (staff or members). I looked at the code and it should work that way, if it doesn't, let me know okay?

Is it possible to adapt this for the WOL page proper?

You mean sort the display of Who's Online (online.php) into a Staff and Members (and Guests?) section as well?

That's possible but that can't be done with this hack, I'd have to write a whole different kind of hack for that. The WOL page works quite a bit differently, more complex and all.....