Text that are in C-style comments, /* like this */, is not exported by export tools. It’s text that’s “in the boneyard”. Unlike other Fountain syntax, these comments can span newlines and other formatting; structurally, it’s as if the text were removed.
This “boneyard” is for text that you’re on the brink of removing, or drafts that you aren’t ready to “uncomment” and include yet, or just anything else you want to ignore.
If you instead just want to annotate your screenplay, Notes or Synopses.