How might I migrate comments from one item type or project to another?

At work (I'm posting on my private account), I have a transition that closes an original item in a JSM project and opens a new item in another project. 

Upon creation of the new item, can there be automation to copy all the comments from the original item into the new comments section or into a new field?  (I would try to use a tab to store the new field, to avoid cluttering up the new item.)  If the solution is a script, and it is simple enough, perhaps you could provide it?