The idea is that the forum is advising that if people are concern for their privacy they have to use TOR but as I said you have to pay for this, so it can be added that additional fees may apply during registration.
Imagine you register an account trough TOR with all that captcha solving for 5-10 min and then suddenly you have to pay. If you don't have/own bitcoin and you don't know how to pay then you probably be disappointed and will never come back.
That's true, I will be disappointed too if this happens to me in another forum.
I recommend adding 2 side notes, one for the possibility of evil fees and its definition, the second of the possibility to count this fee when buying copper membership. I am not sure about this point but I believe I saw it somewhere in the past.