Copying rows down into cells across until row=false

Sorry about the title, let me explain in more detail:

In row A, I have various listings. The title is always in caps, the user is always in mixed case.

For example:

COW
SHEEP
Jim
Bob
Stu
RHINO
Dave
Ollie

So, no-one is interested in COWS but Jim, Bob and Stu like SHEEP. And what I need to end up with is:

COW
SHEEP | Jim, Bob and Stu
RHINO | Dave and Ollie

You get the picture. It doesn't matter if the readers names go into one cell each, I can concatenate them later.

Now, what I've worked out is that I can put a TRUE or a FALSE in the next column along, with:
=IF(AND(LEN(A1)>1,EXACT(A1, UPPER(A1))),TRUE,FALSE)

So I've got

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Now, what I HAD planned on doing was a formula which would test if the cell to the right of A1 said true or false, then concatenate the contents of the cell below the contents of A1 in the most recent TRUE cell, then concatenate that plus the next on and the next one until we get another TRUE. But of course, the cell value changes too.

So I'm clearly out of my depth here! I just showed that to prove that I have at least tried and thought about it, as I know there's worse than a newb posting when they've not even tried!

Thanks, and hello.