An unavoidable question rises: Is Google doing this specifically to Tor users on Bitcointalk?
I doubt it. From my experience: the more often you fail at solving a captcha, or the more captchas you've solved in a small time frame, the harder they get. When you use Tor, you're sharing the same exit node (read: IP) with other users, so all their captcha failures are added to your next captcha difficulty.
By comparison, is Google also refusing to serve CAPTCHAs to Tor users on other sites generally? I wouldnt know. I always use Tor, but I usually boycott sites which try to CAPTCHA me.
I've tried Tor, and it's terrible. And on top of the normal captchas, Cloudflare on many sites adds another captcha. The total process is slow and annoying.
On circuit { 0 /* initial load */, 1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15 }, Google made the familiar allegation of automated queries:
Captchas by now are terrible to solve for humans, while computers get better at it. And a computer has much more patience to solve it!
As a partial solution (I say partial because Cloudflare will still serve you captchas): you can setup your Tor browser to remember your sessions. You could easily create a dedicated Tor-installation that you only use for Bitcointalk, or you can use a private browsing window in Tor when you visit any other site.
PS
I've seen your account in the Copper member thread, and this Copper membership turns out to be an easy way to distinquish between shitposters and serious posters. Not many Newbies post stuff worth reading, well done 