Perhaps the number of spaces between names isn’t that predictable. Here’s an option that’s a little more loosely defined. It’s split into two formulas because the second one uses the first one twice.
The {Step 1}
formula removes the “Clients:” header, replaces any instance of two consecutive spaces with a block of 30 spaces, and trims the result. We’re left with just the names and a big gap of spaces that’s guaranteed to be at least 30 spaces wide (most likely bigger).
TRIM(SUBSTITUTE(SUBSTITUTE(Original, "Clients:", ""), " ", REPT(" ", 30)))
(BTW: depending on how you add code to your post, you can get the forum parser to leave larger space blocks alone. I used the 4-space indentation method above. If you wrap your code in matching graves-triplets, large blocks of spaces are condensed. Learned something new today!)
Here’s what that {Step 1}
output looks like with the field value expanded:
The second formula takes that result and extracts the names by removing 30-character chunks from the beginning and end, and adding the comma in the middle. Because we’re assuming that no name will be 30 characters long, each 30-character extraction returns a name and a portion of the at-least-30-spaces-wide block between names, but none of the other name.
TRIM(LEFT({Step 1}, 30)) & ", " & TRIM(RIGHT({Step 1}, 30))
If you want all of this in a single formula, here you go:
TRIM(LEFT(TRIM(SUBSTITUTE(SUBSTITUTE(Original, "Clients:", ""), " ", REPT(" ", 30))), 30)) & ", " & TRIM(RIGHT(TRIM(SUBSTITUTE(SUBSTITUTE(Original, "Clients:", ""), " ", REPT(" ", 30))), 30))