Also DDoS becomes a problem, and the ways it's done are pretty specific to Tor. Double captchas are necessary when you're getting DDoSed, due to performance reasons. Oh, and captchas are also pretty specific to Tor as well.
There's also a problem of site fronting. Anyone could run a proxy pretending to be you, for arbitrary reasons (not even necessarily the obvious forging and credential stealing). Every site, even a personal blog, has dozens of parasitic fronts, either actively malicious or dormant. You need off-site ways to tell users what is the real address, and provide a smoke test for them (often a part of the address as a picture, for example in a captcha).
>avoid JS for them
Using any JS defies the point and makes your site instantly suspicious.
There's also a problem of site fronting. Anyone could run a proxy pretending to be you, for arbitrary reasons (not even necessarily the obvious forging and credential stealing). Every site, even a personal blog, has dozens of parasitic fronts, either actively malicious or dormant. You need off-site ways to tell users what is the real address, and provide a smoke test for them (often a part of the address as a picture, for example in a captcha).
>avoid JS for them
Using any JS defies the point and makes your site instantly suspicious.