I think the policy could be placed in a more obvious spot. The text in the signup form would probably not be read by some impatient people
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
Pretty much so (mea culpa).
Anyway, the simple fact that there are multiple posts on the web frustrated by this issue (just do a Google search for "bitcointalk can't post") is I believe a sign that an usability problem does exist and it is faced by a non-trivial amount of new users.
What's even worse, this problem most likely disproportionately affects organic new users (such as those coming from Google traffic) which simply want to contribute to a thread they have found. Spammers, scammers and sockpuppets are not really affected since most likely new accounts created for this purpose belong to already existing users.