Need help with printing fields that include large amounts of text

You need to print a list from the comments tables.  Use a Go to Related Records step to find the comments for the ticket, then print the list of comments.  Do not try to print portables.  They are not meant to be printed. 

Why would you want to copy the data to a different field?

Actually, you can print from a layout that has a portal as long as you understand the limitations and they are ones that you can work with for your report. Often, you can't avoid using a portal when you have data from multiple related tables.

OK, but why do YOU want to do the same?

This can be made to work, though I would never use copy and paste script steps to do so. Nor do I use steps that start with Insert when Set Field accomplishes the same result without "breaking" should the target field ever be removed from the layout.

That said, both the List and ExecuteSQL functions may be used to pull data from multiple records of a different table into a single field all in one go.

rgordon's suggestion is the best first approach. Using that method you can size your comments field to be many rows tall but set to slide up/ reduce enclosing part.

The method shown in your script example has it's uses and may be necessary, but it's not the method that should be used if there's a simpler method available that gets the job done.