They can try to block crawlers all they want

They will not succeed without restricting access to Reddit to an unusable degree, since crawlers can be coded to imitate real users close enough. Combine that with enough proxies and they can’t do jack shit

Also you could get arround the Referer header quite easily via redirects (unless Reddit went ahead and used a Whitelist for those, which again would be a very stupid decision) and some more methods