That’s a consideration, yeah, but they’d have to all be hitting lemmy.zip (your instance) and all from the same /32 IPv4 address.

(AFAIK) CG-NAT still uses port address translation so there’s an upper limit to the number of users behind one IP address. They also are distributed geographically. So everyone would need to be in the same area on the same instance to really have that be an issue.

The more likely scenario would be multiple people in the same household using the same instance. But 20 comments per minute, divided by two people in the house would still be 10 comments per minute. That’s still probably more than they could reasonably do.