This is not the spam or vandalism counter-measure, those work differently and only block posting to the sites. And you can avoid them if you establish a reputable account, they won't affect you anymore then.
To your other point, how can one establish a 'reputable account' if it is not even possible to access the site in the first instance.
I don’t understand why Tor users would be interested in reputation at all, given the implicit identification it requires.