Hello @L51723 ,
Since RSVP is built into emails' click reporting functionality, adding comments isn't really something that's going to be available at this time.
With that said, if you're needing to collect comments and non/commitments to your event, and you don't want to setup an event campaign, then I'd advise using survey pages. They have their own reporting, and can allow for selectable character limits for responses.
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