I've never seen anything to suggest comments are supported. I'm sure this list is hardly thorough, but it's something:
DON'T...
...use ampersands (&) anywhere, ever.
...use commas in Parameter values.
...use the Inline HTML 4.0 export format; it doesn't work very well. Use the 3.2 format instead.
DO...
...separate email addresses with commas, not semicolons.
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