Can you instead make heavy limitations for casuals readers? For instance: "3 chapters and 10 comic page views per hour", with a suggestion to register. Kinda like file hosters do.
Crawlers will find a way around registration, but lazy users probably just leave.
That's sort of what's being tried as of now. But the crawlers will simply mask themselves as another and repeat.
Indeed they will figure a way around the registration. But as I've said, it's not to block them out completely. It's to put it to a state where it's manageable. Not every single crawlers will bother to perfect the art of crawling.